Safety of the 2010-11, 2011-12, 2012-13, and 2013-14 seasonal influenza vaccines in pregnancy: Birth defects, spontaneous abortion, preterm delivery, and small for gestational age infants, a study from the cohort arm of VAMPSS

Influenza vaccination during early pregnancy and risk of major birth defects, US Birth Defects Study To Evaluate Pregnancy exposureS, 2014-2019

PURPOSE

Studies of influenza vaccination during pregnancy and major birth defects generally provide reassuring findings. To maintain public confidence, it is important to continue evaluating the safety of maternal vaccination using well characterized, population-based data. This study extended previous research to examine associations between maternal influenza vaccination and selected birth defects using data from the Birth Defects Study To Evaluate Pregnancy exposureS, a US, multisite case-control study.

METHODS

Mothers of case children (diagnosed with a birth defect) and control children (without a birth defect diagnosis) were identified from population-based birth defect surveillance programs and recruited to complete a telephone interview. Data from 2675 case and 1575 control mothers (participants) with deliveries during 2014-2019 were analyzed. Influenza vaccination exposure during the critical exposure period (one month before pregnancy through the first pregnancy month [B1P1] for spina bifida or through the third pregnancy month [B1P3] for other selected birth defects) was assessed controlling for several participant covariates. Logistic regression with propensity score adjustment was used to estimate adjusted odds ratios (aORs) and 95 % confidence intervals (CIs). Several secondary analyses were conducted. A probabilistic bias analysis examined the effect of exposure misclassification.

RESULTS

The aOR observed between B1P1 influenza vaccination exposure and spina bifida was 0.9 (95 % CI: 0.4-2.0). The aORs for B1P3 exposure and other selected birth defects examined ranged from 0.4 to 1.3, with 95 % CIs including the null except those for cleft lip ± cleft palate (aOR: 0.6; 95 % CI: 0.4-0.9) and gastroschisis (aOR: 0.4; 95 % CI: 0.2-0.7). Results from secondary analyses were similar to the primary analyses, and those from probabilistic bias analysis were similar to respective primary and secondary analyses.

CONCLUSION

Findings showed no statistically significant positive associations between influenza vaccination and the selected birth defects, supporting public health efforts to promote optimal vaccination coverage among pregnant women.

Pregnancy loss <28 weeks gestation in maternal influenza and COVID-19 vaccination studies: a review of data sources, 2009-2024

OBJECTIVES

To address gaps in maternal vaccination and pregnancy loss research, large, complex datasets are needed. We aimed to identify and evaluate data sources and data collection methods currently used to capture pregnancy losses <28 weeks following maternal influenza and COVID-19 vaccination research.

STUDY DESIGN

Narrative Review.

METHODS

PubMed, CINAHL, Scopus, and Web of Science were used to identify studies that investigated pregnancy loss <28 gestational weeks following influenza and COVID-19 vaccinations from January 1st, 2009, to March 19th, 2024. Within the resulting studies, the data source(s) used to capture exposure and outcome data were identified and categorised. The capacity to capture and measure exposures, outcomes, and missing data within categories was investigated.

RESULTS

28 articles met the inclusion criteria, representing 1,113,878 participants. Most articles (n = 19) used multiple data sources within the one study, often obtaining exposure and outcome data from separate data sources. Categories of data sources included: registries, adverse reporting systems, medical records, and survey or interview methods.

CONCLUSION

Current data collection practices and existing data sources are adversely impacting data quality, and the ability to combine large datasets necessary for analysing early pregnancy loss risk factors. This also hinders our ability to evaluate the safety of early maternal vaccination and subsequent miscarriage. Establishing pregnancy loss registries using standardised data collection and coding practices, consistent terminology, and accurate exposure and outcome timing is critical. In the absence of registries, we propose an alternative source to capture both pregnancy loss and maternal vaccination data.

Maternal influenza vaccination and associated risk of fetal loss: A claims-based prospective cohort study

BACKGROUND

Although numerous studies support the safety of influenza vaccination during pregnancy, fewer studies have evaluated the risk of miscarriage or considered the effect of prior immunization.

METHODS

Using national de-identified administrative claims data from the Optum Labs Data Warehouse, we conducted a claims-based cohort study of 117,626 pregnancies between January 2009 and December 2018. We identified pandemic A(H1N1)pdm09 and seasonal influenza vaccinations using CPT codes. Fetal loss was defined as miscarriage, medical termination, or stillbirth as identified by ICD-10-CM diagnostic codes. Cox proportional hazard models treating influenza vaccination as a time-varying exposure, weighted for loss-to-follow-up and stratified by baseline probability of vaccination, were used to model the risk of fetal loss by exposure to influenza vaccine.

RESULTS

About 31.4 % of the cohort had a record of influenza vaccination; 10.0 % were vaccinated before pregnancy only, 17.8 % during pregnancy only, and 3.6 % before and during pregnancy. The risk of miscarriage was 39 % lower among those vaccinated during pregnancy compared to unvaccinated (adjusted hazard ratio, aHR 0.61; 95 % CI 0.50, 0.74) and was similar for medical termination or stillbirth (HR 0.69; 95 % CI 0.45, 1.03 and aHR 0.99; 95 % CI 0.76, 1.30, respectively). Similar results were observed for women who received the vaccine before and during pregnancy. We observed little to no association between vaccination before pregnancy and risk of miscarriage (HR 0.98; 95 % CI 0.76, 1.26), medical termination (HR 1.02; 95 % CI 0.46, 2.24), or stillbirth (HR 1.14, 95 % CI 0.77, 1.69).

DISCUSSION

Influenza vaccination was not associated with an increased risk of fetal loss. These results support the safety of influenza vaccine administration even when administered before or early during pregnancy.

Committee on Infectious Diseases, O’Leary ST, Campbell JD, Ardura MI, Bryant KA, Caserta MT, Espinosa C, Frenck RW, Healy CM, John CC, Kourtis AP, Milstone A, Myers A, Pannaraj P, Ratner AJ, Bryant KA, Hofstetter AM, Chaparro JD, Michel JJ, Kimberlin DW, Banerjee R, Barnett ED, Lynfield R, Sawyer MH, Barton-Forbes M, Cardemil CV, Farizo KM, Kafer LM, Moore D, Okeke C, Prestel C, Patel M, Starke JR, Thompson J, Torres JP, Wharton M, Woods CR, Gibbs G. Recommendations for Prevention and Control of Influenza in Children, 2024-2025: Technical Report

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2024 to 2025 season. The rationale for the American Academy of Pediatrics recommendation for annual influenza vaccination of all children without medical contraindications starting at 6 months of age is provided. Influenza vaccination is an important strategy for protecting children and the broader community against influenza. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage and provides detailed guidance on vaccine storage, administration, and implementation. The report also provides a brief background on inactivated (nonlive) and live attenuated influenza vaccines, available vaccines for the 2024-2025 influenza season, vaccination during pregnancy and breastfeeding, diagnostic testing for influenza, and antiviral medications for treatment and chemoprophylaxis. Strategies to promote vaccine uptake are emphasized.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2024-25 Influenza Season

This report updates the 2023-24 recommendations of the Advisory Committee on Immunization Practices (ACIP) concerning the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2022;72[No. RR-2]:1-24). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. Trivalent inactivated influenza vaccines (IIV3s), trivalent recombinant influenza vaccine (RIV3), and trivalent live attenuated influenza vaccine (LAIV3) are expected to be available. All persons should receive an age-appropriate influenza vaccine (i.e., one approved for their age), with the exception that solid organ transplant recipients aged 18 through 64 years who are receiving immunosuppressive medication regimens may receive either high-dose inactivated influenza vaccine (HD-IIV3) or adjuvanted inactivated influenza vaccine (aIIV3) as acceptable options (without a preference over other age-appropriate IIV3s or RIV3). Except for vaccination for adults aged ≥65 years, ACIP makes no preferential recommendation for a specific vaccine when more than one licensed and recommended vaccine is available. ACIP recommends that adults aged ≥65 years preferentially receive any one of the following higher dose or adjuvanted influenza vaccines: trivalent high-dose inactivated influenza vaccine (HD-IIV3), trivalent recombinant influenza vaccine (RIV3), or trivalent adjuvanted inactivated influenza vaccine (aIIV3). If none of these three vaccines is available at an opportunity for vaccine administration, then any other age-appropriate influenza vaccine should be used.Primary updates to this report include the following two topics: the composition of 2024-25 U.S. seasonal influenza vaccines and updated recommendations for vaccination of adult solid organ transplant recipients. First, following a period of no confirmed detections of wild-type influenza B/Yamagata lineage viruses in global surveillance since March 2020, 2024-25 U.S. influenza vaccines will not include an influenza B/Yamagata component. All influenza vaccines available in the United States during the 2024-25 season will be trivalent vaccines containing hemagglutinin derived from 1) an influenza A/Victoria/4897/2022 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/67/2022 (H1N1)pdm09-like virus (for cell culture-based and recombinant vaccines); 2) an influenza A/Thailand/8/2022 (H3N2)-like virus (for egg-based vaccines) or an influenza A/Massachusetts/18/2022 (H3N2)-like virus (for cell culture-based and recombinant vaccines); and 3) an influenza B/Austria/1359417/2021 (Victoria lineage)-like virus. Second, recommendations for vaccination of adult solid organ transplant recipients have been updated to include HD-IIV3 and aIIV3 as acceptable options for solid organ transplant recipients aged 18 through 64 years who are receiving immunosuppressive medication regimens (without a preference over other age-appropriate IIV3s or RIV3).This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2024-25 influenza season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at https://www.cdc.gov/acip-recs/hcp/vaccine-specific/flu.html?CDC_AAref_Val=https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines. Updates and other information are available from CDC's influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Defining and reporting adverse events of special interest in comparative maternal vaccine studies: a systematic review

Introduction

The GAIA (Global Alignment on Immunisation Safety Assessment in Pregnancy) consortium was established in 2014 with the aim of creating a standardised, globally coordinated approach to monitoring the safety of vaccines administered in pregnancy. The consortium developed twenty-six standardised definitions for classifying obstetric and infant adverse events. This systematic review sought to evaluate the current state of adverse event reporting in maternal vaccine trials following the publication of the case definitions by GAIA, and the extent to which these case definitions have been adopted in maternal vaccine safety research.

Methods

A comprehensive search of published literature was undertaken to identify maternal vaccine research studies. PubMed, EMBASE, Web of Science, and Cochrane were searched using a combination of MeSH terms and keyword searches to identify observational or interventional studies that examined vaccine safety in pregnant women with a comparator group. A two-reviewer screening process was undertaken, and a narrative synthesis of the results presented.

Results

14,737 titles were identified from database searches, 435 titles were selected as potentially relevant, 256 were excluded, the remaining 116 papers were included. Influenza vaccine was the most studied (25.0%), followed by TDaP (20.7%) and SARS-CoV-2 (12.9%).Ninety-one studies (78.4%) were conducted in high-income settings. Forty-eight (41.4%) utilised electronic health-records. The majority focused on reporting adverse events of special interest (AESI) in pregnancy (65.0%) alone or in addition to reactogenicity (27.6%). The most frequently reported AESI were preterm birth, small for gestational age and hypertensive disorders. Fewer than 10 studies reported use of GAIA definitions. Gestational age assessment was poorly described; of 39 studies reporting stillbirths 30.8% provided no description of the gestational age threshold.

Conclusions

Low-income settings remain under-represented in comparative maternal vaccine safety research. There has been poor uptake of GAIA case definitions. A lack of harmonisation and standardisation persists limiting comparability of the generated safety data.

Lack of association between COVID-19 vaccines and miscarriage onset using a case-crossover design

Pregnant women might have an increased risk of SARS-COV-2 infection. Although evidence towards the efficacy and safety of COVID-19 is growing still there is room for improvement on the knowledge towards pregnancy adverse events, such as miscarriage. We explored the association of COVID-19 vaccine with the risk of miscarriages using the Real-World. We identified a cohort of vaccinated pregnancies using the BIFAP database which contains systematically recorded data on care patients in Spain (N = 4054). We then restricted it to those women who had a miscarriage using a validated algorithm (N = 607). Among them, we performed a case-crossover design to evaluate the effect of intermittent exposures on the risk of miscarriage. Adjusted Odds Ratio with their confidence intervals were calculated using two analytical approaches: conditional logistic regression and Generalized Linear Mixed-Effects Models. A total of 225 (37.1%) were aged 35-39 years. The most common comorbidities were asthma, migraine, gastritis, and hypothyroidism. A total of 14.7% received only one dose of COVID-19 and 85.3% two doses, respectively. A total of 36.8% of women with one dose and 27.6% with two doses received the vaccine 7 days prior to the miscarriage. Corresponding adjusted estimates for the risk of miscarriage using the conditional logistic regression where as follows: 1.65 (95% CI 0.85-3.23) when using as the sum of 3 control moments among women with one dose, 1.02 (95% CI 0.72-1.46) among women with two doses and 1.03 (95% CI 0.72, 1.46) using the whole study population. Very similar results were obtained when conducting the Generalized Linear Mixed-Effects Models. There was no overall increased risk of miscarriage onset associated with COVID-19 vaccine although contradictory results were found according to the number of doses. Further studies are required with larger sample sizes to assess this association.

COMMITTEE ON INFECTIOUS DISEASES, O’Leary ST, Campbell JD, Ardura MI, Banerjee R, Bryant KA, Caserta MT, Frenck RW, Gerber JS, John CC, Kourtis AP, Myers A, Pannaraj P, Ratner AJ, Shah SS, Bryant KA, Hofstetter AM, Chaparro JD, Michel JJ, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH, Bernstein HH, Cardemil CV, Farizo KM, Kafer LM, Kim D, López Medina E, Moore D, Panagiotakopoulos L, Romero JR, Sauvé L, Starke JR, Thompson J, Wharton M, Woods CR, Frantz JM, Gibbs G. Recommendations for Prevention and Control of Influenza in Children, 2023-2024

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2023-2024 season. The rationale for the American Academy of Pediatrics recommendation for annual influenza vaccination of all children without medical contraindications starting at 6 months of age is provided. Influenza vaccination is an important strategy for protecting children and the broader community against influenza. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage, and provides detailed guidance on vaccine storage, administration, and implementation. The report also provides a brief background on inactivated and live-attenuated influenza vaccines, available vaccines this season, vaccination during pregnancy and breastfeeding, diagnostic testing for influenza, and antiviral medications for treatment and chemoprophylaxis. Strategies to promote vaccine uptake are emphasized.

Safety of influenza vaccination during pregnancy: a systematic review

OBJECTIVE

We conducted a systematic review to evaluate associations between influenza vaccination during pregnancy and adverse birth outcomes and maternal non-obstetric serious adverse events (SAEs), taking into consideration confounding and temporal biases.

METHODS

Electronic databases (Ovid MEDLINE ALL, Embase Classic+Embase and the Cochrane Central Register of Controlled Trials) were searched to June 2021 for observational studies assessing associations between influenza vaccination during pregnancy and maternal non-obstetric SAEs and adverse birth outcomes, including preterm birth, spontaneous abortion, stillbirth, small-for-gestational-age birth and congenital anomalies. Studies of live attenuated vaccines, single-arm cohort studies and abstract-only publications were excluded. Records were screened using a liberal accelerated approach initially, followed by a dual independent approach for full-text screening, data extraction and risk of bias assessment. Pairwise meta-analyses were conducted, where two or more studies met methodological criteria for inclusion. The Grading of Recommendations, Assessment, Development and Evaluation approach was used to assess evidence certainty.

RESULTS

Of 9443 records screened, 63 studies were included. Twenty-nine studies (24 cohort and 5 case-control) evaluated seasonal influenza vaccination (trivalent and/or quadrivalent) versus no vaccination and were the focus of our prioritised syntheses; 34 studies of pandemic vaccines (2009 A/H1N1 and others), combinations of pandemic and seasonal vaccines, and seasonal versus seasonal vaccines were also reviewed. Control for confounding and temporal biases was inconsistent across studies, limiting pooling of data. Meta-analyses for preterm birth, spontaneous abortion and small-for-gestational-age birth demonstrated no significant associations with seasonal influenza vaccination. Immortal time bias was observed in a sensitivity analysis of meta-analysing risk-based preterm birth data. In descriptive summaries for stillbirth, congenital anomalies and maternal non-obstetric SAEs, no significant association with increased risk was found in any studies. All evidence was of very low certainty.

CONCLUSIONS

Evidence of very low certainty suggests that seasonal influenza vaccination during pregnancy is not associated with adverse birth outcomes or maternal non-obstetric SAEs. Appropriate control of confounding and temporal biases in future studies would improve the evidence base.

Risk of Miscarriage in Relation to Seasonal Influenza Vaccination Before or During Pregnancy

OBJECTIVE

To evaluate the association between seasonal influenza vaccination and miscarriage using data from an ongoing, prospective cohort study.

METHODS

We analyzed 2013-2022 data from PRESTO (Pregnancy Study Online), a prospective prepregnancy cohort study of female pregnancy planners and their male partners in the United States and Canada. Female participants completed a baseline questionnaire and then follow-up questionnaires every 8 weeks until pregnancy, during early and late pregnancy, and during the postpartum period. Vaccine information was self-reported on all questionnaires. Miscarriage was identified from self-reported information during follow-up. Male partners were invited to complete a baseline questionnaire only. We used Cox proportional hazard models to estimate the hazard ratio (HR) and 95% CI for the association between vaccination less than 3 months before pregnancy detection through the 19th week of pregnancy and miscarriage, with gestational weeks as the time scale. We modeled vaccination as a time-varying exposure and used propensity-score fine stratification to control for confounding from seasonal and female partner factors.

RESULTS

Of 6,946 pregnancies, 23.3% of female partners reported exposure to influenza vaccine before or during pregnancy: 3.2% during pregnancy (gestational age 4-19 weeks) and 20.1% during the 3 months before pregnancy detection. The miscarriage rate was 16.2% in unvaccinated and 17.0% among vaccinated participants. Compared with no vaccine exposure, influenza vaccination was not associated with increased rate of miscarriage when administered before (HR 0.99, 95% CI 0.81-1.20) or during (HR 0.83, 95% CI 0.47-1.47) pregnancy. Of the 1,135 couples with male partner vaccination data available, 10.8% reported vaccination less than 3 months before pregnancy. The HR for the association between male partner vaccination and miscarriage was 1.17 (95% CI 0.73-1.90).

CONCLUSION

Influenza vaccination before or during pregnancy was not associated with miscarriage.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2023–24 Influenza Season

This report updates the 2022–23 recommendations of the Advisory Committee on Immunization Practices (ACIP) concerning the use of seasonal influenza vaccines in the United States (

MMWR Recomm Rep 2022;71[No. RR-1]:1–28). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. All seasonal influenza vaccines expected to be available in the United States for the 2023–24 season are quadrivalent, containing hemagglutinin (HA) derived from one influenza A(H1N1)pdm09 virus, one influenza A(H3N2) virus, one influenza B/Victoria lineage virus, and one influenza B/Yamagata lineage virus. Inactivated influenza vaccines (IIV4s), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4) are expected to be available.

For most persons who need only 1 dose of influenza vaccine for the season, vaccination should ideally be offered during September or October. However, vaccination should continue after October and throughout the season as long as influenza viruses are circulating and unexpired vaccine is available. Influenza vaccines might be available as early as July or August, but for most adults (particularly adults aged ≥65 years) and for pregnant persons in the first or second trimester, vaccination during July and August should be avoided unless there is concern that vaccination later in the season might not be possible. Certain children aged 6 months through 8 years need 2 doses; these children should receive the first dose as soon as possible after vaccine is available, including during July and August. Vaccination during July and August can be considered for children of any age who need only 1 dose for the season and for pregnant persons who are in the third trimester during these months if vaccine is available

ACIP recommends that all persons aged ≥6 months who do not have contraindications receive a licensed and age-appropriate seasonal influenza vaccine. With the exception of vaccination for adults aged ≥65 years, ACIP makes no preferential recommendation for a specific vaccine when more than one licensed, recommended, and age-appropriate vaccine is available. ACIP recommends that adults aged ≥65 years preferentially receive any one of the following higher dose or adjuvanted influenza vaccines: quadrivalent high-dose inactivated influenza vaccine (HD-IIV4), quadrivalent recombinant influenza vaccine (RIV4), or quadrivalent adjuvanted inactivated influenza vaccine (aIIV4). If none of these three vaccines is available at an opportunity for vaccine administration, then any other age-appropriate influenza vaccine should be used

Primary updates to this report include the following two topics: 1) the composition of 2023–24 U.S. seasonal influenza vaccines and 2) updated recommendations regarding influenza vaccination of persons with egg allergy. First, the composition of 2023–24 U.S. influenza vaccines includes an update to the influenza A(H1N1)pdm09 component. U.S.-licensed influenza vaccines will contain HA derived from 1) an influenza A/Victoria/4897/2022 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/67/2022 (H1N1)pdm09-like virus (for cell culture-based and recombinant vaccines); 2) an influenza A/Darwin/9/2021 (H3N2)-like virus (for egg-based vaccines) or an influenza A/Darwin/6/2021 (H3N2)-like virus (for cell culture-based and recombinant vaccines); 3) an influenza B/Austria/1359417/2021 (Victoria lineage)-like virus; and 4) an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus. Second, ACIP recommends that all persons aged ≥6 months with egg allergy should receive influenza vaccine. Any influenza vaccine (egg based or nonegg based) that is otherwise appropriate for the recipient’s age and health status can be used. It is no longer recommended that persons who have had an allergic reaction to egg involving symptoms other than urticaria should be vaccinated in an inpatient or outpatient medical setting supervised by a health care provider who is able to recognize and manage severe allergic reactions if an egg-based vaccine is used. Egg allergy alone necessitates no additional safety measures for influenza vaccination beyond those recommended for any recipient of any vaccine, regardless of severity of previous reaction to egg. All vaccines should be administered in settings in which personnel and equipment needed for rapid recognition and treatment of acute hypersensitivity reactions are available

This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2023–24 influenza season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at

https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html . These recommendations apply to U.S.-licensed influenza vaccines used according to Food and Drug Administration–licensed indications. Updates and other information are available from CDC’s influenza website ( https://www.cdc.gov/flu ). Vaccination and health care providers should check this site periodically for additional information.

Safety and Protective Effects of Influenza Vaccination in Pregnant Women on Pregnancy and Birth Outcomes in Pune, India: A Cross-Sectional Study

BACKGROUND

Maternal influenza vaccination provides effective protection against influenza infections in pregnant women and their newborns. In India, the influenza vaccine has not yet been offered through immunization programs, owing to the lack of sufficient safety data for pregnant Indian women.

METHODS

This cross-sectional observational study enrolled 558 women admitted to the obstetrics ward of a civic hospital in Pune. Study-related information was obtained from the participants through hospital records and interviews using structured questionnaires. Univariate and multivariable analysis was used, and the chi-square test with adjusted odds ratio was estimated to account for vaccine exposure and the temporal nature of each outcome, respectively.

RESULTS

Women not vaccinated against influenza during pregnancy had a higher risk of delivering very LBW infants, and possible protective effects were suggested (AOR 2.29, 95% CI 1.03 to 5.58, p = 0.03). No association was observed between maternal influenza vaccination for Caesarean section (LSCS) (AOR 0.97, 95% CI, 0.78, 1.85), stillbirth (AOR 1.8, 95% CI 0.18, 24.64) and NICU admission (AOR, 0.87, 0.29 to 2.85), and congenital anomaly (AOR, 0.81, 0.10 to 3.87).

INTERPRETATION

These results show that the influenza vaccine administered during pregnancy is safe and might lower the risk of negative birth outcomes.

The perinatal health challenges of emerging and re-emerging infectious diseases: A narrative review

The world has seen numerous infectious disease outbreaks in the past decade. In many cases these outbreaks have had considerable perinatal health consequences including increased risk of preterm delivery (e.g., influenza, measles, and COVID-19), and the delivery of low birth weight or small for gestational age babies (e.g., influenza, COVID-19). Furthermore, severe perinatal outcomes including perinatal and infant death are a known consequence of multiple infectious diseases (e.g., Ebola virus disease, Zika virus disease, pertussis, and measles). In addition to vaccination during pregnancy (where possible), pregnant women, are provided some level of protection from the adverse effects of infection through community-level application of evidence-based transmission-control methods. This review demonstrates that it takes almost 2 years for the perinatal impacts of an infectious disease outbreak to be reported. However, many infectious disease outbreaks between 2010 and 2020 have no associated pregnancy data reported in the scientific literature, or pregnancy data is reported in the form of case-studies only. This lack of systematic data collection and reporting has a negative impact on our understanding of these diseases and the implications they may have for pregnant women and their unborn infants. Monitoring perinatal health is an essential aspect of national and global healthcare strategies as perinatal life has a critical impact on early life mortality as well as possible effects on later life health. The unpredictable nature of emerging infections and the potential for adverse perinatal outcomes necessitate that we thoroughly assess pregnancy and perinatal health implications of disease outbreaks and their public health interventions in tandem with outbreak response efforts. Disease surveillance programs should incorporate perinatal health monitoring and health systems around the world should endeavor to continuously collect perinatal health data in order to quickly update pregnancy care protocols as needed.

The risk of major structural birth defects associated with seasonal influenza vaccination during pregnancy: A population-based cohort study

INTRODUCTION

Seasonal inactivated influenza vaccine (IIV) is routinely recommended during pregnancy to protect both mothers and infants from complications following influenza infection. While previous studies have evaluated the risk of major structural birth defects in infants associated with prenatal administration of monovalent pandemic IIV, fewer studies have evaluated the risk associated with prenatal seasonal IIV.

METHODS

We conducted a population-based cohort study of 125,866 singleton births between 2012 and 2016 in Western Australia. Birth registrations were linked to the state's registers for congenital anomalies and a state prenatal vaccination database. We estimated prevalence ratios (PR) of any major structural birth defect and defects by organ system. Vaccinated pregnancies were defined as those with a record of IIV in the first trimester. Inverse probability treatment weighting factored for baseline probability for vaccination. A Bonferroni correction was applied to account for multiple comparisons.

RESULTS

About 3.9% of births had a major structural birth defect. Seasonal IIV exposure during the first trimester was not associated with diagnosis of any major structural birth defect diagnosed within 1 month of birth (PR 0.98, 95% CI: 0.77, 1.28) or within 6 years of life (PR 1.02, 95% CI: 0.78, 1.35). We identified no increased risk in specific birth defects associated with seasonal IIV.

CONCLUSION

Based on registry data for up to 6 years of follow-up, results suggest there is no association between maternal influenza vaccination and risk of major structural birth defects. These results support the safety of seasonal IIV administration during pregnancy.

Recommendations for Prevention and Control of Influenza in Children, 2022-2023

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2022 to 2023 season. The American Academy of Pediatrics recommends annual influenza vaccination of all children without medical contraindications starting at 6 months of age. Influenza vaccination is an important strategy for protecting children and the broader community as well as reducing the overall burden of respiratory illnesses when other viruses, including severe acute respiratory syndrome-coronavirus 2, are cocirculating. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage, and provides detailed guidance on storage, administration, and implementation. The report also provides a brief background on inactivated and live attenuated influenza vaccine recommendations, vaccination during pregnancy and breastfeeding, diagnostic testing, and antiviral medications for treatment and chemoprophylaxis. Updated information is provided about the 2021 to 2022 influenza season, influenza immunization rates, the effectiveness of influenza vaccination on hospitalization and mortality, available vaccines, guidance for patients with history of severe allergic reactions to prior influenza vaccinations, and strategies to promote vaccine uptake.

Outcomes in Pregnant Persons Immunized with a Cell-Based Quadrivalent Inactivated Influenza Vaccine: A Prospective Observational Cohort Study

Objective: To evaluate pregnancy and infant outcomes among persons immunized with a cell-based quadrivalent inactivated influenza vaccine (IIV4c) during routine pregnancy care. Design: Prospective observational cohort. Setting: US-based obstetrics/gynecology clinics. Population: Pregnant persons. This US-based, prospective observational cohort study evaluated the safety of quadrivalent inactivated influenza vaccine (IIV4c; Flucelvax® Quad) in pregnant persons immunized over 3 influenza seasons between 2017 and 2020. Pregnant persons were immunized with IIV4c as part of routine care, after which their health care provides HCPs with all observational data to a single coordinating center. Follow-up data were collected at the end of the second trimester and/or at the time of pregnancy outcome. A scientific advisory committee reviewed the data. Prevalence point estimates were reported with 95% confidence intervals (CIs). Pregnancy outcomes included: live birth, stillbirth, spontaneous abortion, elective termination, and maternal death. Infant outcomes included: preterm birth (<37 weeks gestational age), low birth weight (<2500 g), or major congenital malformations (MCMs). Of the 665 evaluable participants, 659 (99.1%) had a live birth. No stillbirths (0% [95% CI 0.0−0.6]), 4 spontaneous abortions (1.9% [0.5−4.8]), and 1 elective termination (0.5% [0.0−2.6]) were reported. Among 673 infants, 9.2% (upper 95% CI 11.5%) were born prematurely, 5.8% (upper 95% CI 7.6%) had low birth weight, and 1.9% (upper 95% CI 3.1%) were reported to have an MCM. No maternal deaths were reported. Of the 2 infants who died shortly after birth, one was adjudicated as not related to the vaccine; the other’s cause could not be determined due to maternal loss to follow-up. The prevalence of adverse pregnancy outcomes or preterm birth, low birth weight, or MCMs in newborns was similar in persons vaccinated with IIV4c compared to the rates observed in US surveillance systems. The safety profile of IIV4c in pregnant persons is consistent with previously studied influenza vaccines.

A Prospective Cohort Study on Pregnancy Outcomes of Persons Immunized with a Seasonal Quadrivalent Inactivated Influenza Vaccine during Pregnancy

This US-based, prospective observational cohort study evaluated the safety of a quadrivalent inactivated influenza vaccine (IIV4; Afluria Quadrivalent) in pregnant persons immunized over four influenza seasons between 2017 and 2021. Pregnancy outcomes included live birth, stillbirth, spontaneous abortion, and elective termination. Infant events of interest were major congenital malformations (MCMs), preterm birth (<37 weeks gestational age), and low birth weight (LBW). Data were descriptive; prevalence point estimates were reported with 95% confidence intervals (CI). A total of 483 pregnant persons were given IIV4 and evaluated; 477 (98.8%) reported a live birth, and there were 2 stillbirths, 4 spontaneous abortions, and no elective terminations or maternal deaths. The prevalence rates of infant events were as follows: preterm birth, 7.2% (upper 95% CI, 9.6%); LBW, 5.4% (upper 95% CI, 7.4%); and MCMs, 0.8% (upper 95% CI, 1.9%). Point estimates and upper 95% CIs of the observed prevalence rates were lower than or similar to background prevalence in the general US population. Our findings suggest no evidence of a safety concern with vaccinating this group at high risk of influenza complications and are consistent with published data from databases and surveillance systems that monitor the safety of influenza vaccines in pregnant persons.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2022-23 Influenza Season

This report updates the 2021–22 recommendations of the Advisory Committee on Immunization Practices (ACIP) concerning the use of seasonal influenza vaccines in the United States

(MMWR Recomm Rep 2021;70[No. RR-5]:1–24). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used.With the exception of vaccination for adults aged ≥65 years, ACIP makes no preferential recommendation for a specific vaccine when more than one licensed, recommended, and age-appropriate vaccine is available. All seasonal influenza vaccines expected to be available in the United States for the 2022–23 season are quadrivalent, containing hemagglutinin (HA) derived from one influenza A(H1N1)pdm09 virus, one influenza A(H3N2) virus, one influenza B/Victoria lineage virus, and one influenza B/Yamagata lineage virus. Inactivated influenza vaccines (IIV4s), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4) are expected to be available. Trivalent influenza vaccines are no longer available, but data that involve these vaccines are included for reference.

Influenza vaccines might be available as early as July or August, but for most persons who need only 1 dose of influenza vaccine for the season, vaccination should ideally be offered during September or October. However, vaccination should continue after October and throughout the season as long as influenza viruses are circulating and unexpired vaccine is available. For most adults (particularly adults aged ≥65 years) and for pregnant persons in the first or second trimester, vaccination during July and August should be avoided unless there is concern that vaccination later in the season might not be possible. Certain children aged 6 months through 8 years need 2 doses; these children should receive the first dose as soon as possible after vaccine is available, including during July and August. Vaccination during July and August can be considered for children of any age who need only 1 dose for the season and for pregnant persons who are in the third trimester if vaccine is available during those months

Updates described in this report reflect discussions during public meetings of ACIP that were held on October 20, 2021; January 12, 2022; February 23, 2022; and June 22, 2022. Primary updates to this report include the following three topics: 1) the composition of 2022–23 U.S. seasonal influenza vaccines; 2) updates to the description of influenza vaccines expected to be available for the 2022–23 season, including one influenza vaccine labeling change that occurred after the publication of the 2021–22 ACIP influenza recommendations; and 3) updates to the recommendations concerning vaccination of adults aged ≥65 years. First, the composition of 2022–23 U.S. influenza vaccines includes updates to the influenza A(H3N2) and influenza B/Victoria lineage components. U.S.-licensed influenza vaccines will contain HA derived from an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus (for cell culture–based or recombinant vaccines); an influenza A/Darwin/9/2021 (H3N2)-like virus (for egg-based vaccines) or an influenza A/Darwin/6/2021 (H3N2)-like virus (for cell culture–based or recombinant vaccines); an influenza B/Austria/1359417/2021 (Victoria lineage)-like virus; and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus. Second, the approved age indication for the cell culture–based inactivated influenza vaccine, Flucelvax Quadrivalent (ccIIV4), was changed in October 2021 from ≥2 years to ≥6 months. Third, recommendations for vaccination of adults aged ≥65 years have been modified. ACIP recommends that adults aged ≥65 years preferentially receive any one of the following higher dose or adjuvanted influenza vaccines: quadrivalent high-dose inactivated influenza vaccine (HD-IIV4), quadrivalent recombinant influenza vaccine (RIV4), or quadrivalent adjuvanted inactivated influenza vaccine (aIIV4). If none of these three vaccines is available at an opportunity for vaccine administration, then any other age-appropriate influenza vaccine should be used

This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2022–23 influenza season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at

https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used according to Food and Drug Administration–licensed indications. Updates and other information are available from CDC’s influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Influenza vaccination during pregnancy and risk of selected major structural noncardiac birth defects, National Birth Defects Prevention Study 2006-2011

PURPOSE

To assess associations between influenza vaccination during etiologically-relevant windows and selected major structural non-cardiac birth defects.

STUDY DESIGN

We analyzed data from the National Birth Defects Prevention Study, a multisite, population-based case-control study, for 8233 case children diagnosed with a birth defect and 4937 control children without a birth defect with delivery dates during 2006-2011. For all analyses except for neural tube defects (NTDs), we classified mothers who reported influenza vaccination 1 month before through the third pregnancy month as exposed; the exposure window for NTDs was 1 month before through the first pregnancy month. For defects with five or more exposed case children, we used logistic regression to estimate propensity score-adjusted odds ratios (aORs) and 95% confidence intervals (CIs), adjusting for estimated delivery year and season; plurality; maternal age, race/ethnicity, smoking and alcohol use, low folate intake; and, for NTDs, folate antagonist medications.

RESULTS

There were 334 (4.1%) case and 197 (4.0%) control mothers who reported influenza vaccination from 1 month before through the third pregnancy month. Adjusted ORs ranged from 0.53 for omphalocele to 1.74 for duodenal atresia/stenosis. Most aORs (11 of 19) were ≤1 and all adjusted CIs included the null. The unadjusted CIs for two defects, hypospadias and craniosynostosis, excluded the null. These estimates were attenuated upon covariate adjustment (hypospadias aOR: 1.25 (95% CI 0.89, 1.76); craniosynostosis aOR: 1.23 (95% CI: 0.88, 1.74)).

CONCLUSIONS

Results for several non-cardiac major birth defects add to the existing evidence supporting the safety of inactivated influenza vaccination during pregnancy. Under-reporting of vaccination may have biased estimates downward.

Characteristics and Outcomes of Hospitalized Pregnant Women With Influenza, 2010 to 2019 : A Repeated Cross-Sectional Study

BACKGROUND

Pregnant women may be at increased risk for severe influenza-associated outcomes.

OBJECTIVE

To describe characteristics and outcomes of hospitalized pregnant women with influenza.

DESIGN

Repeated cross-sectional study.

SETTING

The population-based U.S. Influenza Hospitalization Surveillance Network during the 2010-2011 through 2018-2019 influenza seasons.

PATIENTS

Pregnant women (aged 15 to 44 years) hospitalized with laboratory-confirmed influenza identified through provider-initiated or facility-based testing practices.

MEASUREMENTS

Clinical characteristics, interventions, and in-hospital maternal and fetal outcomes were obtained through medical chart abstraction. Multivariable logistic regression was used to evaluate the association between influenza A subtype and severe maternal influenza-associated outcomes, including intensive care unit (ICU) admission, mechanical ventilation, extracorporeal membrane oxygenation, or in-hospital death.

RESULTS

Of 9652 women aged 15 to 44 years and hospitalized with influenza, 2690 (27.9%) were pregnant. Among the 2690 pregnant women, the median age was 28 years, 62% were in their third trimester, and 42% had at least 1 underlying condition. Overall, 32% were vaccinated against influenza and 88% received antiviral treatment. Five percent required ICU admission, 2% required mechanical ventilation, and 0.3% (n = 8) died. Pregnant women with influenza A H1N1 were more likely to have severe outcomes than those with influenza A H3N2 (adjusted risk ratio, 1.9 [95% CI, 1.3 to 2.8]). Most women (71%) were still pregnant at hospital discharge. Among 754 women who were no longer pregnant at discharge, 96% had a pregnancy resulting in live birth, and 3% experienced fetal loss.

LIMITATION

Maternal and fetal outcomes that occurred after hospital discharge were not captured.

CONCLUSION

Over 9 influenza seasons, one third of reproductive-aged women hospitalized with influenza were pregnant. Influenza A H1N1 was associated with more severe maternal outcomes. Pregnant women remain a high-priority target group for vaccination.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention.

Seasonal Influenza Vaccination During Pregnancy and the Risk of Major Congenital Malformations in Live-born Infants: A 2010-2016 Historical Cohort Study

BACKGROUND

Available evidence indicates that seasonal inactivated influenza vaccination during pregnancy protects both the mother and her newborn and is safe. Nevertheless, ongoing safety assessments are important in sustaining vaccine uptake. Few studies have explored safety in relation to major congenital malformations (MCMs), particularly in the first trimester when most organogenesis occurs.

METHODS

Anonymized UK primary care data (the Clinical Practice Research Datalink), including a recently developed Pregnancy Register, were used to identify live-born singletons delivered between 2010 and 2016. Maternal influenza vaccination was determined using primary care records and stratified by trimester. Ascertainment of MCMs from infant primary care records was maximized by linkage to hospitalization data and death certificates. The relationship between vaccination and MCMs recorded in the year after delivery and in early childhood was then assessed using multivariable Cox regression.

RESULTS

A total of 78 150 live-birth pregnancies were identified: 6872 (8.8%) were vaccinated in the first trimester, 11 678 (14.9%) in the second, and 12 931 (16.5%) in the third. Overall, 5707 live births resulted in an infant with an MCM recorded in the year after delivery and the adjusted hazard ratio when comparing first-trimester vaccination to no vaccination was 1.06 (99% CI, .94-1.19; P = .2). Results were similar for second- and third-trimester vaccination and for analyses considering MCMs recorded beyond the first birthday.

CONCLUSIONS

In this large, population-based historical cohort study there was no evidence to suggest that seasonal influenza vaccine was associated with MCMs when given in the first trimester or subsequently in pregnancy.

History of pandemic H1N1-containing influenza vaccination and risk for spontaneous abortion and birth defects

BACKGROUND

One recent study suggested an association between receipt of pandemic H1N1 (pH1N1)-containing vaccines in consecutive influenza seasons and spontaneous abortion, but corroborating scientific evidence is limited. In the present study, we leveraged a population of vaccine-compliant pregnant military women to examine history of pH1N1-containing influenza vaccination and adverse pregnancy outcomes. Because seasonal influenza vaccination is compulsory for military service, safety concerns regarding repeat vaccination are particularly relevant in this population.

METHODS

Pregnancies and live births from Department of Defense Birth and Infant Health Research program data were linked with military personnel immunization records to identify women vaccinated with a pH1N1-containing vaccine in pregnancy prior to 21 6/7 weeks' gestation, October 2009-April 2015. Cox and modified Poisson regression models estimated associations between vaccination with pH1N1- versus non-pH1N1-containing influenza vaccine in the season prior to the index pregnancy, and spontaneous abortion and birth defects, respectively. Cox models were calculated for two periods of follow-up: through (1) 21 6/7 weeks' gestation and (2) 28 days postvaccination.

RESULTS

Of 26,264 pregnancies, 21,736 (82.8%) were among women who received a dose of pH1N1-containing vaccine in the prior influenza season and 4,528 (17.2%) were among women who received non-pH1N1-containing vaccine in the prior influenza season. Among 23,121 infants, 19,365 (83.8%) and 3,756 (16.2%) had mothers exposed and unexposed to pH1N1-containing vaccine in the prior influenza season, respectively. The adjusted hazard ratio (aHR) for spontaneous abortion approximated 1.0 across the complete follow-up period (95% confidence interval [CI]: 0.89-1.13) and was slightly elevated when censored at 28 days postvaccination, though the CI was imprecise (aHR: 1.19; 95% CI: 0.97-1.46). No associations with birth defects were observed.

CONCLUSION

This work lends additional safety evidence and support for vaccination against pH1N1 in pregnancy, regardless of the vaccine received in the prior influenza season.

Recommendations for Prevention and Control of Influenza in Children, 2021-2022

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of the influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2021-2022 season. Influenza vaccination is an important intervention to protect vulnerable populations and reduce the burden of respiratory illnesses during circulation of severe acute respiratory syndrome coronavirus 2, which is expected to continue during this influenza season. In this technical report, we summarize recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, vaccination coverage, and detailed guidance on storage, administration, and implementation. We also provide background on inactivated and live attenuated influenza vaccine recommendations, vaccination during pregnancy and breastfeeding, diagnostic testing, and antiviral medications for treatment and chemoprophylaxis.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021-22 Influenza Season

This report updates the 2020-21 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2020;69[No. RR-8]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used. ACIP makes no preferential recommendation for a specific vaccine when more than one licensed, recommended, and age-appropriate vaccine is available. During the 2021-22 influenza season, the following types of vaccines are expected to be available: inactivated influenza vaccines (IIV4s), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4).The 2021-22 influenza season is expected to coincide with continued circulation of SARS-CoV-2, the virus that causes COVID-19. Influenza vaccination of persons aged ≥6 months to reduce prevalence of illness caused by influenza will reduce symptoms that might be confused with those of COVID-19. Prevention of and reduction in the severity of influenza illness and reduction of outpatient visits, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate stress on the U.S. health care system. Guidance for vaccine planning during the pandemic is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html. Recommendations for the use of COVID-19 vaccines are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/covid-19.html, and additional clinical guidance is available at https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html.Updates described in this report reflect discussions during public meetings of ACIP that were held on October 28, 2020; February 25, 2021; and June 24, 2021. Primary updates to this report include the following six items. First, all seasonal influenza vaccines available in the United States for the 2021-22 season are expected to be quadrivalent. Second, the composition of 2021-22 U.S. influenza vaccines includes updates to the influenza A(H1N1)pdm09 and influenza A(H3N2) components. U.S.-licensed influenza vaccines will contain hemagglutinin derived from an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus (for cell culture-based and recombinant vaccines), an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus, an influenza B/Washington/02/2019 (Victoria lineage)-like virus, and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus. Third, the approved age indication for the cell culture-based inactivated influenza vaccine, Flucelvax Quadrivalent (ccIIV4), has been expanded from ages ≥4 years to ages ≥2 years. Fourth, discussion of administration of influenza vaccines with other vaccines includes considerations for coadministration of influenza vaccines and COVID-19 vaccines. Providers should also consult current ACIP COVID-19 vaccine recommendations and CDC guidance concerning coadministration of these vaccines with influenza vaccines. Vaccines that are given at the same time should be administered in separate anatomic sites. Fifth, guidance concerning timing of influenza vaccination now states that vaccination soon after vaccine becomes available can be considered for pregnant women in the third trimester. As previously recommended, children who need 2 doses (children aged 6 months through 8 years who have never received influenza vaccine or who have not previously received a lifetime total of ≥2 doses) should receive their first dose as soon as possible after vaccine becomes available to allow the second dose (which must be administered ≥4 weeks later) to be received by the end of October. For nonpregnant adults, vaccination in July and August should be avoided unless there is concern that later vaccination might not be possible. Sixth, contraindications and precautions to the use of ccIIV4 and RIV4 have been modified, specifically with regard to persons with a history of severe allergic reaction (e.g., anaphylaxis) to an influenza vaccine. A history of a severe allergic reaction to a previous dose of any egg-based IIV, LAIV, or RIV of any valency is a precaution to use of ccIIV4. A history of a severe allergic reaction to a previous dose of any egg-based IIV, ccIIV, or LAIV of any valency is a precaution to use of RIV4. Use of ccIIV4 and RIV4 in such instances should occur in an inpatient or outpatient medical setting under supervision of a provider who can recognize and manage a severe allergic reaction; providers can also consider consulting with an allergist to help identify the vaccine component responsible for the reaction. For ccIIV4, history of a severe allergic reaction (e.g., anaphylaxis) to any ccIIV of any valency or any component of ccIIV4 is a contraindication to future use of ccIIV4. For RIV4, history of a severe allergic reaction (e.g., anaphylaxis) to any RIV of any valency or any component of RIV4 is a contraindication to future use of RIV4. This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2021-22 influenza season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used according to Food and Drug Administration-licensed indications. Updates and other information are available from CDC's influenza website (https://www.cdc.gov/flu); vaccination and health care providers should check this site periodically for additional information.

Implementation of a Mandatory Influenza Vaccine Policy: A 10-Year Experience

BACKGROUND

Influenza vaccination of healthcare workers (HCWs) has been recommended for more than 30 years. In 2009, HCWs were designated as a priority group by the Centers for Disease Control and Prevention. Current HCW vaccination rates are 78% across all settings and reach approximately 92% among those employed in hospital settings. Over the last decade, it has become clear that mandatory vaccine policies result in maximal rates of HCW immunization.

METHODS

In this observational 10-year study, we describe the implementation of a mandatory influenza vaccination policy in a dedicated quaternary pediatric hospital setting by a multidisciplinary team. We analyzed 10 years of available data from deidentified occupational health records from 2009-2010 through the 2018-2019 influenza seasons. Descriptive statistics were performed using Stata v15 and Excel.

RESULTS

Sustained increases in HCW immunization rates above 99% were observed in the 10 years postimplementation, in addition to a reduction in exemption requests and healthcare-associated influenza. In the year of implementation, 145 (1.6%) HCWs were placed on temporary suspension for failure to receive the vaccine without documentation of an exemption, with 9 (0.06%) subsequently being terminated. Since then, between 0 and 3 HCWs are terminated yearly for failure to receive the vaccine.

CONCLUSIONS

Implementation of our mandatory influenza vaccination program succeeded in successfully increasing the proportion of immunized HCWs at a quaternary care children's hospital, reducing annual exemption requests with a small number of terminations secondary to vaccine refusal. Temporal trends suggest a positive impact on the safety of our patients.

One "misunderstood" health issue: demonstrating and communicating the safety of influenza a vaccination in pregnancy: a systematic review and meta-analysis

Background

The American College of Obstetricians and Gynecologists (ACOG) makes certain recommendations including the annual influenza vaccination of pregnant and pre-pregnant women during influenza (flu) season with an inactivated influenza vaccine as soon as it becomes available. The Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices in association with ACOG state that the vaccine is safe to be given any trimester during pregnancy. However, due to a lack of communication, the public is unaware of the effects of influenza A vaccination in pregnancy. Since this is a vital public health concern, we aimed to communicate with evidence, the safety of influenza A vaccination in pregnancy in order to improve the rate of influenza A vaccines in pregnant women.

Methods

This health communication issue was based on the impact of influenza vaccine on fetal outcomes. Therefore, a search was carried out through medical-based online databases including: Cochrane Central, EMBASE, Web of Science, MEDLINE, http://www.ClinicalTrials.gov, and Google scholar for relevant English-based publications. Adverse fetal outcomes were considered as the endpoints of this analysis. The most specific RevMan 5.3 (latest version) software was used to carry out this analysis. Risk ratios (RR) with 95% confidence intervals (CI) were involved in data and results representation and interpretation.

Results

A total number of 679, 992 pregnant women participated in this analysis. Based on this current analysis, premature/preterm birth (< 37 weeks) was significantly reduced in pregnant women who were vaccinated for influenza A (RR: 0.80, 95% CI: 0.69–0.92; P = 0.002) as compared to those women who were not vaccinated. Similarly, influenza A vaccination decreased the risk for very preterm birth (< 32 weeks) (RR: 0.70, 95% CI: 0.58–0.84; P = 0.0001). The risks for infants with low birth weight (RR: 0.71, 95% CI: 0.49–1.04; P = 0.08), very low birth weight (RR: 0.69, 95% CI: 0.23–2.11; P = 0.52) and infants small for gestational age (RR: 0.93, 95% CI: 0.83–1.05; P = 0.26) were not increased with the vaccine. Influenza A vaccination was not associated with increased risks of stillbirth (RR: 0.63, 95% CI: 0.38–1.03; P = 0.07), birth defects (RR: 0.67, 95% CI: 0.26–1.72; P = 0.41), admission to neonatal intensive care unit or Apgar score < 7 in 5 min.

Conclusion

Influenza vaccine is completely safe in pregnancy. It significantly lowers premature birth and is not associated with any serious adverse neonatal outcome. Hence, this important piece of information should be communicated and conveyed to all pregnant women, for a safer and healthier pregnancy. At last, this public health issue should further be addressed to the population through media and other communication means in order to improve the rate of influenza A vaccines in pregnant women for a healthier and more productive population.

Developing algorithms for identifying major structural birth defects using automated electronic health data

PURPOSE

Given the 2015 transition to International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnostic coding, updates to our previously published algorithms for major structural birth defects (BDs) were necessary. Aims of this study were to update, validate, and refine algorithms for identifying selected BDs, and then to use these algorithms to describe BD prevalence in the vaccine safety datalink (VSD) population.

METHODS

We converted our ICD-9-CM list of selected BDs to ICD-10-CM using available crosswalks with manual review of codes. We identified, chart reviewed, and adjudicated a sample of infants in the VSD with ≥2 ICD-10-CM diagnoses for one of seven common BDs. Positive predictive values (PPVs) were calculated; for BDs with suboptimal PPV, algorithms were refined. Final automated algorithms were applied to a cohort of live births delivered 10/1/2015-9/30/2017 at eight VSD sites to estimate BD prevalence. This research was approved by the HealthPartners Institutional Review Board, by all participating VSD sites, and by the CDC, with a waiver of informed consent.

RESULTS

Of 573 infants with ≥2 diagnoses for a targeted BD, on adjudication, we classified 399 (69.6%) as probable cases, 31 (5.4%) as possible cases and 143 (25.0%) as not having the targeted BD. PPVs for the final BD algorithms ranged from 0.76 (hypospadias) to 1.0 (gastroschisis). Among 212 857 births over 2 years following transition to ICD-10-CM coding, prevalence for the full list of selected defects in the VSD was 1.8%.

CONCLUSIONS

Algorithms can identify infants with selected BDs using automated healthcare data with reasonable accuracy. Our updated algorithms can be used in observational studies of maternal vaccine safety and may be adapted for use in other surveillance systems.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2020-21 Influenza Season

This report updates the 2019–20 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2019;68[No. RR-3]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4) are expected to be available. Most influenza vaccines available for the 2020–21 season will be quadrivalent, with the exception of MF59-adjuvanted IIV, which is expected to be available in both quadrivalent and trivalent formulations.

Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 23, 2019; February 26, 2020; and June 24, 2020. Primary updates to this report include the following two items. First, the composition of 2020–21 U.S. influenza vaccines includes updates to the influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B/Victoria lineage components. Second, recent licensures of two new influenza vaccines, Fluzone High-Dose Quadrivalent and Fluad Quadrivalent, are discussed. Both new vaccines are licensed for persons aged ≥65 years. Additional changes include updated discussion of contraindications and precautions to influenza vaccination and the accompanying Table, updated discussion concerning use of LAIV4 in the setting of influenza antiviral medication use, and updated recommendations concerning vaccination of persons with egg allergy who receive either cell culture–based IIV4 (ccIIV4) or RIV4.

The 2020–21 influenza season will coincide with the continued or recurrent circulation of SARS-CoV-2 (the novel coronavirus associated with coronavirus disease 2019 [COVID-19]). Influenza vaccination of persons aged ≥6 months to reduce prevalence of illness caused by influenza will reduce symptoms that might be confused with those of COVID-19. Prevention of and reduction in the severity of influenza illness and reduction of outpatient illnesses, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate stress on the U.S. health care system. Guidance for vaccine planning during the pandemic is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html.

This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2020–21 season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used within Food and Drug Administration (FDA)–licensed indications. Updates and other information are available from CDC’s influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Determinants of pregnant women's knowledge about influenza and the influenza vaccine: A large, single-centre cohort study

Introduction

Although influenza can lead to adverse outcomes during pregnancy, the level of influenza vaccine coverage among pregnant women remains very low. According to the literature, a high level of knowledge about influenza disease and the influenza vaccine is one of the main determinants of vaccination coverage. The objective of the present study was to describe pregnant women’s level of knowledge of these topics and to identify any corresponding determinants.

Material and methods

A prospective, observational, hospital-based study of women having given birth in our university medical centre during the 2014–2015 influenza season. Data were collected through a self-questionnaire or extracted from medical records. Determinants of highest knowledge were identified using logistic regression.

Results

Of the 2069 women included in the study, 827 (40%) did not know that influenza can lead to severe adverse outcomes for the mother, and 960 (46%) did not know about possible severe adverse outcomes for the baby. Two hundred and one women (9.8%) stated that the vaccine was “contraindicated” or “unnecessary” during pregnancy. Only 205 women (17%) had been vaccinated during a previous pregnancy. Determinants of the highest level of knowledge were age over 24, a high educational level, previous influenza vaccination, nulliparity, and the recommendation of vaccination by a healthcare professional.

Conclusions

Recommending vaccination during pregnancy appears to increase knowledge about influenza and its vaccine among pregnant women.

Safety of influenza vaccination on adverse birth outcomes among pregnant women: A prospective cohort study in Japan

BACKGROUND

Pregnant women are in the highest priority group for receiving influenza vaccination. However, they may be reluctant to receive the vaccination due to concerns about the influence of vaccination on the fetuses.

METHODS

This prospective cohort study of 10 330 pregnant women examined the safety of influenza vaccination in terms of adverse birth outcomes. Influenza vaccination during pregnancy was determined from questionnaires before and after the 2013/2014 influenza season. All subjects were followed until the end of their pregnancy. Adverse birth outcomes, including miscarriage, stillbirth, preterm birth, low birth weight, and malformation, were assessed by obstetrician reports.

RESULTS

Adverse birth outcomes were reported for 641 (10%) of the 6387 unvaccinated pregnant women and 356 (9%) of the 3943 vaccinated pregnant women. Even after adjusting for potential confounders, vaccination during pregnancy showed no association with the risk of adverse birth outcomes (odds ratio 0.90, 95% confidence interval 0.76-1.07). Vaccination during the first or second trimester displayed no association with adverse birth outcomes, whereas vaccination during the third trimester was associated with a decreased risk of adverse birth outcomes (odds ratio 0.70, 95% confidence interval 0.51-0.98).

CONCLUSIONS

Influenza vaccination during pregnancy did not increase the risk of adverse birth outcomes, regardless of the trimester in which vaccination was performed, when compared to unvaccinated pregnant women.

Determinants of influenza vaccination uptake in pregnancy: a large single-Centre cohort study

BACKGROUND

Although vaccination of pregnant women against influenza is recommended, the vaccination rate remains low. We conducted a study to identify determinants of influenza vaccination uptake in pregnancy in order to identify strategies to improve seasonal influenza vaccination rates.

METHODS

Prospective observational hospital-based study in the French hospital performing the highest number of deliveries, located in the city of Lille, among all women who had given birth during the 2014-2015 influenza season. Data were collected through a self-completed questionnaire and from medical files. The vaccination uptake was self-reported. Determinants of vaccination uptake were identified using logistic regression analysis.

RESULTS

Of the 2045 women included in the study, 35.5% reported that they had been vaccinated against influenza during their pregnancy. The principal factors significantly associated with greater vaccination uptake were previous influenza vaccination (50.9% vs 20.2%, OR 4.1, 95% CI 3.1-5.5), nulliparity (41.0% vs 31.3%, OR 2.5, 95% CI 1.7-3.7), history of preterm delivery < 34 weeks (43.4% vs 30.3%, OR 2.3, 95% CI 1.1-4.9), the mother's perception that the frequency of vaccine complications for babies is very low (54.6% vs 20.6%, OR 1.1, 95% CI 0.5-2.2), the mother's good knowledge of influenza and its vaccine (61.7% vs 24.4%, OR 3.1, 95% CI 2.2-4.4), hospital-based prenatal care in their first trimester of pregnancy (55.0% vs 30.2%, OR 2.1, 95% CI 1.2-3.7), vaccination recommendations during pregnancy by a healthcare worker (47.0% vs 2.7%, OR 18.8, 95% CI 10.0-35.8), receipt of a vaccine reimbursement form (52.4% vs 18.6%, OR 2.0, 95% CI 1.5-2.7), and information from at least one healthcare worker about the vaccine (43.8% vs 19.1%, OR 1.8, 95% CI 1.3-2.6).

CONCLUSIONS

Our findings suggest that in order to increase flu vaccination compliance among pregnant women, future public health programmes must ensure cost-free access to vaccination, and incorporate education about the risks of influenza and the efficacy/safety of vaccination and clear recommendations from healthcare professionals into routine antenatal care.

The fetal origins of mental illness

The impact of infections and inflammation during pregnancy on the developing fetal brain remains incompletely defined, with important clinical and research gaps. Although the classic infectious TORCH pathogens (ie, Toxoplasma gondii, rubella virus, cytomegalovirus [CMV], herpes simplex virus) are known to be directly teratogenic, emerging evidence suggests that these infections represent the most extreme end of a much larger spectrum of injury. We present the accumulating evidence that prenatal exposure to a wide variety of viral and bacterial infections-or simply inflammation-may subtly alter fetal brain development, leading to neuropsychiatric consequences for the child later in life. The link between influenza infections in pregnant women and an increased risk for development of schizophrenia in their children was first described more than 30 years ago. Since then, evidence suggests that a range of infections during pregnancy may also increase risk for autism spectrum disorder and depression in the child. Subsequent studies in animal models demonstrated that both pregnancy infections and inflammation can result in direct injury to neurons and neural progenitor cells or indirect injury through activation of microglia and astrocytes, which can trigger cytokine production and oxidative stress. Infectious exposures can also alter placental serotonin production, which can perturb neurotransmitter signaling in the developing brain. Clinically, detection of these subtle injuries to the fetal brain is difficult. As the neuropsychiatric impact of perinatal infections or inflammation may not be known for decades after birth, our construct for defining teratogenic infections in pregnancy (eg, TORCH) based on congenital anomalies is insufficient to capture the full adverse impact on the child. We discuss the clinical implications of this body of evidence and how we might place greater emphasis on prevention of prenatal infections. For example, increasing uptake of the seasonal influenza vaccine is a key strategy to reduce perinatal infections and the risk for fetal brain injury. An important research gap exists in understanding how antibiotic therapy during pregnancy affects the fetal inflammatory load and how to avoid inflammation-mediated injury to the fetal brain. In summary, we discuss the current evidence and mechanisms linking infections and inflammation with the increased lifelong risk of neuropsychiatric disorders in the child, and how we might improve prenatal care to protect the fetal brain.

The Importance of Vaccinating Children and Pregnant Women against Influenza Virus Infection

Influenza virus infection is responsible for significant morbidity and mortality in the pediatric and pregnant women populations, with deaths frequently caused by severe influenza-associated lower respiratory tract infection and acute respiratory distress syndrome (ARDS). An appropriate immune response requires controlling the viral infection through activation of antiviral defenses, which involves cells of the lung and immune system. High levels of viral infection or high levels of inflammation in the lower airways can contribute to ARDS. Pregnant women and young children, especially those born prematurely, may develop serious complications if infected with influenza virus. Vaccination against influenza will lead to lower infection rates and fewer complications, even if the vaccine is poorly matched to circulating viral strains, with maternal vaccination offering infants protection via antibody transmission through the placenta and breast milk. Despite the health benefits of the influenza vaccine, vaccination rates around the world remain well below targets. Trust in the use of vaccines among the public must be restored in order to increase vaccination rates and decrease the public health burden of influenza.

Maternal tetanus, diphtheria, and acellular pertussis (Tdap) and influenza immunization: an overview

BACKGROUND

Maternal tetanus, diphtheria, and acellular pertussis (Tdap) and influenza immunization for women during pregnancy (the so-called "maternal immunization") has been introduced in several countries, and recently also in Italy, to protect mother and fetus during pregnancy, infant in his first months of life and mother during postpartum period. However, very low vaccination coverage rates have been reached due to several variables.

METHODS

A literature search was conducted on PubMed and Embase, including any experimental or observational studies, to assesses existing evidence on the effectiveness, efficacy, safety and optimal timing of administration of Tdap and influenza immunization in pregnancy for mothers and their infants. The search was finalized in August 2019.

RESULTS

Reviewing the literature, we identified only a few studies that, among several maternal and infant outcomes, found sporadic significant associations with maternal influenza immunization and even less with Tdap immunization. Moreover, most of the authors of these studies explained these findings as a result of residual confounding effect. The effectiveness of maternal influenza immunization is more complicated to prove than the effectiveness of Tdap immunization because of several reasons. Not all nations recommend and offer vaccines in the same weeks of pregnancy and this one manifests the complexity in defining the best timing for Tdap or influenza immunization.

CONCLUSIONS

The safety of maternal Tdap or influenza immunization is supported by the evidence so far, however, regular surveillance should be maintained, especially with regard to the influenza vaccine that changes in formulation each year. There is a need to optimize the timing of vaccination in pregnancy and to have a national system of detection of maternal immunization in each country.

Birth outcomes in women who have taken adalimumab in pregnancy: A prospective cohort study

BACKGROUND

Information is needed on the safety of adalimumab when used in pregnancy for the treatment of certain autoimmune diseases.

METHODS AND FINDINGS

Between 2004 and 2016, the Organization of Teratology Information Specialists Research Center at the University of California San Diego conducted a prospective controlled observational cohort study in 602 pregnant women who had or had not taken adalimumab. Women in the adalimumab-exposed cohort had received at least one dose of the drug in the first trimester for the treatment of rheumatoid arthritis or Crohn's Disease (N = 257). Women in the disease comparison cohort had not used adalimumab in pregnancy (N = 120). Women in the healthy comparison cohort had no rheumatic or inflammatory bowel diseases (N = 225). Women and their infants were followed to one year postpartum with maternal interviews, medical records abstraction, and physical examinations. Study outcomes were major structural birth defects, minor defects, spontaneous abortion, preterm delivery, pre and post-natal growth deficiency, serious or opportunistic infections and malignancies. 42/602 (7.0%) of pregnancies were lost-to-follow-up. 22/221 (10.0%) in the adalimumab-exposed cohort had a live born infant with a major birth defect compared to 8/106 (7.5%) in the diseased unexposed cohort (adjusted odds ratio 1.10, 95% confidence interval [CI] 0.45 to 2.73). Women in the adalimumab-exposed cohort were more likely to deliver preterm compared to the healthy cohort (adjusted hazard ratio [aHR] 2.59, 95% CI 1.22 to 5.50), but not compared to the diseased unexposed cohort (aHR 0.82, 95% CI 0.66 to 7.20). No significant increased risks were noted with adalimumab exposure for any other study outcomes.

CONCLUSIONS

Adalimumab exposure in pregnancy compared to diseased unexposed pregnancies was not associated with an increased risk for any of the adverse outcomes examined. Women with rheumatoid arthritis or Crohn's Disease were at increased risk of preterm delivery, irrespective of adalimumab exposure.

Recommendations for Prevention and Control of Influenza in Children, 2019-2020

This statement updates the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccines and antiviral medications in the prevention and treatment of influenza in children during the 2019-2020 season. The American Academy of Pediatrics continues to recommend routine influenza immunization of all children without medical contraindications, starting at 6 months of age. Any licensed, recommended, age-appropriate vaccine available can be administered, without preference of one product or formulation over another. Antiviral treatment of influenza with any licensed, recommended, age-appropriate influenza antiviral medication continues to be recommended for children with suspected or confirmed influenza, particularly those who are hospitalized, have severe or progressive disease, or have underlying conditions that increase their risk of complications of influenza.

Inactivated influenza vaccine and spontaneous abortion in the Vaccine Safety Datalink in 2012-13, 2013-14, and 2014-15

Introduction:

A recent study reported an association between inactivated influenza vaccine (IIV) and spontaneous abortion (SAB), but only among women who had also been vaccinated in the previous influenza season. We sought to estimate the association between IIV administered in three recent influenza seasons and SAB among women who were and were not vaccinated in the previous influenza season.

Methods:

We conducted a case-control study over three influenza seasons (2012–13, 2013–14, 2014–15) in the Vaccine Safety Datalink (VSD). Cases (women with SAB) and controls (women with live births) were matched on VSD site, date of last menstrual period, age group, and influenza vaccination status in the previous influenza season. Of 1908 presumptive cases identified from the electronic record, 1236 were included in the main analysis. Administration of IIV was documented in several risk windows, including 1–28, 29–56, and >56 days before the SAB date.

Results:

Among 627 matched pairs vaccinated in the previous season, no association was found between vaccination in the 1–28 day risk window and SAB (adjusted odds ratio (aOR) 0.9; 95% confidence interval (CI) 0.6–1.5). The season-specific aOR ranged from 0.5 to 1.7 with all CIs including the null value of 1.0. Similarly, no association was found among women who were not vaccinated in the previous season; the season-specific aOR in the 1–28 day risk window ranged from 0.6 to 0.7 and the 95% CI included 1.0 in each season. There was no association found between SAB and influenza vaccination in the other risk windows, or when vaccine receipt was analyzed relative to date of conception.

Conclusion:

During these seasons we found no association between IIV and SAB, including among women vaccinated in the previous season. These findings lend support to current recommendations for influenza vaccination at any time during pregnancy, including the first trimester.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2019-20 Influenza Season

This report updates the 2018-19 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2018;67[No. RR-3]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. A licensed, recommended, and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2019-20 season. Standard-dose, unadjuvanted, inactivated influenza vaccines will be available in quadrivalent formulations (IIV4s). High-dose (HD-IIV3) and adjuvanted (aIIV3) inactivated influenza vaccines will be available in trivalent formulations. Recombinant (RIV4) and live attenuated influenza vaccine (LAIV4) will be available in quadrivalent formulations.Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 25, 2018; February 27, 2019; and June 27, 2019. Primary updates in this report include the following two items. First, 2019-20 U.S. trivalent influenza vaccines will contain hemagglutinin (HA) derived from an A/Brisbane/02/2018 (H1N1)pdm09-like virus, an A/Kansas/14/2017 (H3N2)-like virus, and a B/Colorado/06/2017-like virus (Victoria lineage). Quadrivalent influenza vaccines will contain HA derived from these three viruses, and a B/Phuket/3073/2013-like virus (Yamagata lineage). Second, recent labeling changes for two IIV4s, Afluria Quadrivalent and Fluzone Quadrivalent, are discussed. The age indication for Afluria Quadrivalent has been expanded from ≥5 years to ≥6 months. The dose volume for Afluria Quadrivalent is 0.25 mL for children aged 6 through 35 months and 0.5 mL for all persons aged ≥36 months (≥3 years). The dose volume for Fluzone Quadrivalent for children aged 6 through 35 months, which was previously 0.25 mL, is now either 0.25 mL or 0.5 mL. The dose volume for Fluzone Quadrivalent is 0.5 mL for all persons aged ≥36 months (≥3 years).This report focuses on the recommendations for use of vaccines for the prevention and control of influenza during the 2019-20 season in the United States. A brief summary of these recommendations and a Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used within Food and Drug Administration-licensed indications. Updates and other information are available from CDC's influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Measurement of birth outcomes in analyses of the impact of maternal influenza vaccination

Background

The estimated association of maternal influenza vaccination and birth outcomes may be sensitive to methods used to define preterm birth or small‐for‐gestational age (SGA).

Methods

In a cohort of pregnant women in Lao People's Democratic Republic, we estimated gestational age from: (a) date of last menstrual period (LMP), (b) any prenatal ultrasound, (c) first trimester ultrasound, (d) Ballard Score at delivery, and (e) an algorithm combining LMP and ultrasound. Infants were classified as SGA at birth using a Canadian, global, and equation‐based growth reference. We estimated the association of maternal influenza vaccination and birth outcomes, by influenza activity, using multivariable log‐binomial regression and Cox proportional hazards regression with vaccination as a time‐varying exposure.

Results

The frequency of preterm birth in the cohort varied by method to estimate gestational age, from 5% using Ballard Score to 15% using any ultrasound. Using LMP, any ultrasound, or the algorithm, we found statistically significant reductions in preterm birth among vaccinated women during periods of high influenza activity and statistically significant increases in SGA, using a Canadian growth reference. We did not find statistically significant associations with SGA when using global or equation‐based growth references.

Conclusions

The association of maternal influenza vaccination and birth outcomes was most affected by the choice of a growth reference used to define SGA at birth. The association with pre‐term birth was present and consistent across multiple statistical approaches. Future studies of birth outcomes, specifically SGA, should carefully consider the potential for bias introduced by measurement choice.

Effects of maternal influenza vaccination on adverse birth outcomes: A systematic review and Bayesian meta-analysis

BACKGROUND

Although pregnant women are a priority group for influenza vaccination, its effect on birth outcomes has long been debated. Numerous observational studies and a few randomized controlled studies have been conducted, with inconsistent results.

OBJECTIVES

To evaluate the association of influenza vaccination in pregnancy with adverse birth outcomes.

DATA SOURCE

The Cochrane Library, PubMed, EMBASE, Web of Science, and Scopus were searched.

STUDY ELIGIBILITY CRITERIA

This analysis included randomized placebo-controlled studies, cohort studies, and case-control studies, in which inactivated influenza vaccination was given during pregnancy and fetal adverse birth outcomes were assessed.

PARTICIPANTS & INTERVENTION

Women who received inactivated influenza vaccine during pregnancy and their offspring.

STUDY APPRAISAL AND SYNTHESIS

Two independent reviewers and a third reviewer collaborated in study selection and data extraction. A Bayesian 3-level random-effects model was utilized to assess the impact of maternal influenza vaccination on birth outcomes, which were presented as odds ratios (ORs) with 95% credible interval (CrIs). Bayesian outcome probabilities (P) of an OR<1 were calculated, and values of at least 90% (0.9) were deemed to indicate a significant result.

RESULTS

Among the 6,249 identified publications, 48 studies were eligible for the meta-analysis, including 2 randomized controlled trials, 41 cohort studies, and 5 case-control studies. The risk of none of the following adverse birth outcomes decreased significantly: preterm birth (OR = 0.945, 95% CrI: 0.736-1.345, P = 73.3%), low birth weight (OR = 0.928, 95% CrI: 0.432-2.112, P = 76.7%), small for gestational age (OR = 0.971, 95% CrI: 0.249-4.217,P = 63.3%), congenital malformation (OR = 1.026, 95% CrI: 0.687-1.600, P = 38.0%), and fetal death (OR = 0.942, 95% CrI: 0.560-1.954, P = 61.6%). Summary estimates including only cohort studies showed significantly decreased risks for preterm birth, small for gestational age and fetal death. However, after adjusting for season at the time of vaccination and countries' income level, only fetal death remained significant.

CONCLUSION

This Bayesian meta-analysis did not find a protective effect of maternal influenza vaccination against adverse birth outcomes, as reported in previous studies. In fact, our results showed evidence of null associations between maternal influenza vaccination and adverse birth outcomes.

Influenza Vaccination, Pregnancy Safety, and Risk of Early Pregnancy Loss

Since 2004, the Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists have recommended routine influenza vaccination for all pregnant women in any trimester. Maternal influenza vaccination has been shown to decrease the risk of influenza and its complications among pregnant women and their infants in the first 6 months of life. In a recent article published in Vaccine, Donahue and colleagues reported a possible association between influenza vaccination when given very early in the first trimester and spontaneous abortion. There are limited conclusions that should be drawn from this study given the case-control design as well as the small number of patients included in the subanalysis that is the basis for the report. A prior first-trimester safety study from this group, using a similar study design, had not observed any association with spontaneous abortion, and other reports of first-trimester vaccine safety have not observed an association. The lack of a biologically plausible mechanism for the suggested association between previous influenza vaccination and early pregnancy loss is of concern. The study's reported observation is not definitive and needs be replicated in appropriately designed studies before changing clinical practice. Pregnant women are at high risk for severe influenza-related complications, including death, and health care providers have an obligation to their patients to continue to recommend and provide influenza vaccinations.

The safety of inactivated influenza vaccines in pregnancy for birth outcomes: a systematic review

Pregnant women are at increased risk of morbidity and mortality from influenza and are recognized as a priority group for influenza vaccination. Despite this, uptake is often poor and one reason cited for this is concerns about safety. The objective of this study was to perform a systematic review of the safety of inactivated influenza vaccination (IIV) in pregnancy. Studies were included if they were: (i) observational or experimental design; (ii) included a comparator group comprising of unvaccinated pregnant women; (iii) comprised of either seasonal IIV or monovalent H1N1 IIV (including adjuvanted vaccines); and (iv) addressed one of the following outcomes: preterm birth (PTB), small for gestational age (SGA), fetal death (including stillbirth or spontaneous abortion), low birth weight (LBW) or congenital abnormalities. Two reviewers screened abstracts and titles and selected full texts for retrieval. Crude odds ratios were calculated from reported event rates, using binomial standard errors. Adjusted odds ratios, hazard ratios and relative rates were extracted as reported in each paper. After removal of duplicates and full text eligibility assessment, 40 studies remained. The aOR for PTB was 0.87 (0.78–0.96), for LBW 0.82 (0.76–0.89), congenital abnormality 1.03 (0.99–1.07), SGA 0.99 (0.94–1.04) and stillbirth 0.84 (0.65–1.08). This study contributes to the increasing body of safety data for IIV in pregnancy and reports a protective effect on PTB and LBW.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices-United States, 2018-19 Influenza Season

This report updates the 2017-18 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2017;66[No. RR-2]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. A licensed, recommended, and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2018-19 season. Standard-dose, unadjuvanted, inactivated influenza vaccines will be available in quadrivalent (IIV4) and trivalent (IIV3) formulations. Recombinant influenza vaccine (RIV4) and live attenuated influenza vaccine (LAIV4) will be available in quadrivalent formulations. High-dose inactivated influenza vaccine (HD-IIV3) and adjuvanted inactivated influenza vaccine (aIIV3) will be available in trivalent formulations.Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 25, 2017; February 21, 2018; and June 20, 2018. New and updated information in this report includes the following four items. First, vaccine viruses included in the 2018-19 U.S. trivalent influenza vaccines will be an A/Michigan/45/2015 (H1N1)pdm09-like virus, an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus, and a B/Colorado/06/2017-like virus (Victoria lineage). Quadrivalent influenza vaccines will contain these three viruses and an additional influenza B vaccine virus, a B/Phuket/3073/2013-like virus (Yamagata lineage). Second, recommendations for the use of LAIV4 (FluMist Quadrivalent) have been updated. Following two seasons (2016-17 and 2017-18) during which ACIP recommended that LAIV4 not be used, for the 2018-19 season, vaccination providers may choose to administer any licensed, age-appropriate influenza vaccine (IIV, RIV4, or LAIV4). LAIV4 is an option for those for whom it is appropriate. Third, persons with a history of egg allergy of any severity may receive any licensed, recommended, and age-appropriate influenza vaccine (IIV, RIV4, or LAIV4). Additional recommendations concerning vaccination of egg-allergic persons are discussed. Finally, information on recent licensures and labeling changes is discussed, including expansion of the age indication for Afluria Quadrivalent (IIV4) from ≥18 years to ≥5 years and expansion of the age indication for Fluarix Quadrivalent (IIV4), previously licensed for ≥3 years, to ≥6 months.This report focuses on the recommendations for use of vaccines for the prevention and control of influenza during the 2018-19 season in the United States. A Background Document containing further information and a brief summary of these recommendations are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html.These recommendations apply to U.S.-licensed influenza vaccines used within Food and Drug Administration-licensed indications. Updates and other information are available at CDC's influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check CDC's influenza website periodically for additional information.