Effect of influenza vaccination in the first trimester of pregnancy

Safety of quadrivalent recombinant influenza vaccine in pregnant persons and their infants

Background

The Advisory Committee on Immunization Practices (ACIP) and the American College of Obstetricians and Gynecologists (ACOG) recommend that all pregnant persons receive any licensed, recommended, and age-appropriate inactivated influenza vaccine (SD-IIV) or recombinant influenza vaccine (RIV) to protect against influenza and influenza-related complications. RIV was safe and efficacious in pre- and postlicensure studies, however there is limited RIV safety data in pregnant persons.

Objective

To evaluate the safety of quadrivalent recombinant influenza vaccine (RIV4) versus a quadrivalent standard-dose, inactivated influenza (SD-IIV4) in a large cohort of pregnant persons and their infants.

Study Design

This postlicensure observational safety study conducted at Kaiser Permanente Northern California evaluated the subset of pregnant persons vaccinated in routine care as part of a larger cluster-randomized vaccine effectiveness study comparing RIV4 vs. SD-IIV4 (ClinicalTrials.gov NCT03694392). We identified pregnancy (spontaneous abortion, preterm labor, stillbirth/fetal death, congenital/fetal anomalies detected during pregnancy, eclampsia/pre-eclampsia, placental abruption), birth (preterm birth, low birth weight, small for gestational age), and neonatal/infant outcomes (infant death, failure to thrive, congenital anomalies detected after delivery) using diagnostic codes among pregnant persons ≥18 years immunized with RIV4 or SD-IIV4 during the 2018/19 and 2019/20 influenza seasons and their infants. We used conditional logistic regression adjusted for age group, race, ethnicity, trimester of influenza vaccination, comorbidities, and BMI, stratified by gestational age to estimate the odds ratio (OR) of pregnancy outcomes following vaccination with RIV4 vs. SD-IIV4. Using logistic regression, we separately estimated the adjusted OR of birth and neonatal/infant outcomes in the first year of life (eg, death) in infants of RIV4 vs. SD-IIV4 vaccinated pregnant persons.

Results

The study population included 48,781 pregnant persons (RIV4 = 14,981; SD-IIV4 = 33,800) and 47,394 live births (RIV4 = 14,538; SD-IIV4 = 32,856). There was no statistical difference in any pregnancy outcome or in birth and neonatal/infant outcome between RIV4 vs. SD-IIV4 vaccinated pregnant persons and their infants.

Conclusion

Compared with receipt of a SD-IIV4 during pregnancy, this large study did not identify any pregnancy, birth, or neonatal/infant safety concerns following receipt of a RIV4 during pregnancy and demonstrates that the safety of RIV4 in pregnancy was similar to SD-IIV4. This study provides additional evidence regarding the safety of influenza vaccination in pregnant persons and further supports ACIP and ACOG recommendations that all pregnant persons receive an inactivated or recombinant influenza vaccine.

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.

Influvac Tetra: clinical experience on safety, efficacy, and immunogenicity

INTRODUCTION

This paper summarizes the safety and immunogenicity data of Influvac Tetra across all age groups starting from 6 months of age, obtained during its clinical development program.

AREAS COVERED

The article covers the clinical development program of Influvac Tetra based on five registration studies that included different age groups, different comparators, and participants from Europe and Asia. Safety and immunogenicity were assessed in all studies and in one study, the efficacy of Influvac Tetra was assessed.

EXPERT OPINION

Seasonal influenza is a vaccine-preventable disease that can cause serious complications. Several types of influenza vaccines are available, including egg-based (standard dose, high dose, and adjuvanted), cell-based, and recombinant. The COVID-19 pandemic has stimulated innovation in the development such as mRNA vaccines. However, these vaccines are still in development and the true value still has to be proven. Regardless of the type of vaccine, it is also important to increase overall vaccination coverage. ECDC recommends that EU Member States implement action plans and policies aimed at reaching 75% coverage in at-risk groups and healthcare workers. Even so, vaccine coverage is still far from recommended.

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.

Maternal Vaccination to Prevent Adverse Pregnancy Outcomes: An Underutilized Molecular Immunological Intervention?

Adverse pregnancy outcomes including maternal mortality, stillbirth, preterm birth, intrauterine growth restriction cause millions of deaths each year. More effective interventions are urgently needed. Maternal immunization could be one such intervention protecting the mother and newborn from infection through its pathogen-specific effects. However, many adverse pregnancy outcomes are not directly linked to the infectious pathogens targeted by existing maternal vaccines but rather are linked to pathological inflammation unfolding during pregnancy. The underlying pathogenesis driving such unfavourable outcomes have only partially been elucidated but appear to relate to altered immune regulation by innate as well as adaptive immune responses, ultimately leading to aberrant maternal immune activation. Maternal immunization, like all immunization, impacts the immune system beyond pathogen-specific immunity. This raises the possibility that maternal vaccination could potentially be utilised as a pathogen-agnostic immune modulatory intervention to redirect abnormal immune trajectories towards a more favourable phenotype providing pregnancy protection. In this review we describe the epidemiological evidence surrounding this hypothesis, along with the mechanistic plausibility and present a possible path forward to accelerate addressing the urgent need of adverse pregnancy outcomes.

Vaccine Hesitancy in Women's Health

The development of vaccines is considered one of the greatest breakthroughs of modern medicine, saving millions of lives around the world each year. Despite vaccines' proven success, vaccine hesitancy remains a major issue affecting vaccine uptake. Common themes exist in patients' apprehension to receive vaccines. Women's health providers possess an important role in addressing these concerns and dispelling common misconceptions that may increase vaccine hesitancy thereby reduce vaccine uptake. This review aims to explore many of these topics as they are related to women's health and provide strategies for providers to implement which may reduce vaccine hesitancy among our patients.

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.

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.

Efficacy of a Smartphone Application to Promote Maternal Influenza Vaccination: A Randomized Controlled Trial

The maternal vaccine coverage rate has been low in Taiwan. We developed an “Influenza Vaccination Reminder Application” and evaluated its efficacy in improving vaccination intention among pregnant women in Taiwan. A randomized controlled trial was conducted to compare the positive change in vaccination intention between the experimental group and the control group. Pregnant women who were more than 20 years old and at less than 32 weeks of gestation were recruited from four regional hospitals in southern Taiwan during November 2020 to April 2021. Pregnant women were randomly assigned to the experimental group, to whom the “Influenza Vaccination Reminder Application” was provided for at least two months, while pregnant women in the control group received regular maternal education only. The differences in knowledge about influenza and its vaccines, attitudes towards maternal influenza vaccination, and behavior intention of influenza vaccination among pregnant women before and after the experiment intervention were compared between two groups. The results included 126 women in the experimental group and 117 women in the control group and showed that the “Influenza Vaccination Reminder Application” increased pregnant women’s knowledge about influenza and vaccines (percentage increase in the experimental group and control group: 11.64% vs. 7.39%), strengthened their positive attitudes towards maternal influenza vaccination (percentage increase: 5.39% vs. 1.44%), and promoted positive behavioral intention toward influenza vaccination (proportion of participants with positive change in vaccination intention: 17.46% vs. 7.69%). The study supports use of “Influenza Vaccination Reminder Application” to promote the behavior intention of influenza vaccination among pregnant women in Taiwan.

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.

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.

Monitoring of Influenza Vaccination Coverage among Pregnant Women in Germany Based on Nationwide Outpatient Claims Data: Findings for Seasons 2014/15 to 2019/20

Pregnant women and their infants are at increased risk for severe influenza-related complications. A decade has passed since influenza vaccination was first recommended for pregnant women in Germany in 2010; however, monitoring of vaccination coverage (VC) has not yet been implemented for this target group. Using nationwide outpatient claims data, we here provide results on influenza VC among pregnant women in Germany for seasons 2014/15 to 2019/20. For any given season, pregnant women were defined as women who had undergone prenatal health care in at least two consecutive quarters within a season. VC increased from 9.0% in season 2014/15 to 16.6% in 2019/20 (+84%), while most of the increase occurred from season 2016/17 (VC: 9.9%) onwards (+68%). Consistently across seasons, women in east Germany were 40 to 60% more likely to be vaccinated compared to women residing in west Germany. According to age, the highest VC was observed among women aged 35 to <40 years (2019/20: 18.2%). Despite noticeable increases in influenza VC during recent years, overall coverage remains low among pregnant women. Starting with this analysis, VC among pregnant women in Germany will be monitored on a yearly basis in order to detect trends and identify immunization gaps.

Experience and attitudes on vaccinations recommended during pregnancy: survey on an Italian sample of women and consultant gynecologists

Active immunization in pregnancy is recommended for the influenza and the tetanus, diphtheria, and acellular pertussis (Tdap) vaccines. Evidence indicates vaccine effectiveness in preventing influenza-related hospitalizations and pertussis in early infancy. We investigate vaccine uptake in pregnant and non-pregnant women through a sample of young women and consultant gynecologists, along with the potential predisposing and/or enabling factors affecting attitudes to vaccination (knowledge, beliefs, barriers). A cross-sectional study was conducted between June and September 2019, with a sample of 251 women and 14 consultant gynecologists at the Local Health Authority (ASL01) of the Abruzzo Region (Italy), using an anonymous, self-report questionnaire survey. Among the participants, 5.6% of women had received influenza vaccination, 16.4% had received Tdap during pregnancy and only 1.2% had received both vaccines. The assessment of the psychometric attitudinal variables has suggested a more positive willingness to receive Tdap than influenza vaccine among women, as the former is considered more important for the maternal and neonatal health. Health care workers have reported vaccine safety concerns, lack of information, and misconceptions about the need for vaccination as barriers to immunization in pregnant women. The results of this study will contribute to defining the goals and strategies to increase vaccine uptake under the current recommendations, through promoting effective training programs for all health care workers involved (gynecologists, obstetricians, public health physicians).

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.

Risk of adverse maternal and foetal outcomes associated with inactivated influenza vaccination in first trimester of pregnancy

BACKGROUND

In many countries, influenza vaccination is routinely recommended during any stage of pregnancy, yet uptake remains low, particularly in the first trimester. This is thought to be due to maternal concerns regarding vaccine safety.

OBJECTIVE

To evaluate the safety of influenza vaccination in the first trimester of pregnancy.

METHODS

In a 4-year retrospective cohort study using probabilistic record linkage of administrative health data, we established a population-based cohort of 2391 women vaccinated in first trimester and 68 447 never vaccinated women with a date of conception between 2012 and 2015 in Western Australia. We estimated the relative risk (RR) of perinatal health outcomes among first trimester vaccinated women as compared to never vaccinated women using log-binomial logistic regression following a propensity score matched (PSM) analyses (2391 vaccinated women matched with 9564 never vaccinated women).

RESULTS

First trimester vaccination was not associated with increased risk of stillbirth (RR 1.18, 95% confidence interval [CI] 0.64, 2.19), small for gestational age (RR 0.96, 95% CI 0.83, 1.11) or preeclampsia (RR 0.97, 95% CI 0.74, 1.28). The risk of spontaneous birth at 32-36 weeks was higher in first trimester vaccinated women compared with never vaccinated women (RR 1.40, 95% CI 1.11, 1.77). Vaccination was associated with a 10-19% increase in the risk of gestational diabetes (RR 1.18, 95% CI 0.94, 1.49), premature rupture of membranes (RR 1.10, 95% CI 0.82, 1.48), and threatened preterm labour (RR 1.19, 95% CI 0.90, 1.59).

CONCLUSIONS

With exception to spontaneous preterm birth, findings suggest that first trimester vaccination is not associated with adverse maternal and foetal outcomes. Results can be used to support patient and provider-level vaccine decision making during first trimester.

Evaluating the Association of Stillbirths After Maternal Vaccination in the Vaccine Safety Datalink

OBJECTIVE

To evaluate whether the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommended influenza and tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccinations in pregnancy are associated with increased risk of stillbirth.

METHODS

We performed a case-control study in the Vaccine Safety Datalink that was matched 1:4 on site, month, and year of last menstrual period, comparing the odds of vaccination in pregnancies that ended in stillbirth (defined as fetal loss at or after 20 weeks of gestation) compared with those that ended in live birth from January 1, 2012, to September 30, 2015. We included patients with singleton pregnancies that ended in stillbirth or live birth who had at least one prenatal care visit, pregnancy dating information, and continuous health plan enrollment for the duration of pregnancy. Medical records for all stillbirths were reviewed. We were statistically powered to detect an odds ratio (OR) of 1.37 when evaluating the association between influenza or Tdap vaccination and stillbirth. We also examined stillbirth rates in pregnant patients aged 14-49 years in the Vaccine Safety Datalink between 2007 and 2015.

RESULTS

In our matched analysis of 795 confirmed stillbirths in the case group and 3,180 live births in the control group, there was no significant association between influenza vaccination during pregnancy and stillbirth (343/795 [43.1%] stillbirths in the case group vs 1,407/3,180 [44.3%] live births in the control group, OR 0.94, adjusted OR 0.95, 95% CI 0.79-1.14, P=.54) and no significant association between Tdap vaccination during pregnancy and stillbirth (184/795 [23.1%] stillbirths in the case group vs 746/3,180 [23.5%] live births in the control group, OR 0.97, aOR 0.96, 95% CI 0.76-1.28, P=.91). From 2007 to 2015, the stillbirth rate in the Vaccine Safety Datalink was 5.2 per 1,000 live births and stillbirths.

CONCLUSION

No association was found between vaccination during pregnancy and the odds of stillbirth. These findings support the safety of ACIP recommendations for vaccination during pregnancy.

Seasonal Influenza Vaccine in Pregnant Women: Views and Experiences of Obstetrician-Gynecologists

Background: Seasonal influenza vaccination rates among pregnant women remain well below the Healthy People 2020 target of 80%. Obstetrician-gynecologist (OB/GYN) recommendations are a critical means of encouraging pregnant women to get vaccinated, but there are limited data about their views. Materials and Methods: A nationally representative survey of 506 practicing OB/GYNs was completed between October 26, 2015, and May 8, 2016. Analyses included univariate distributions and comparisons based on age, size of practice, and academic affiliation using all-pairs, dependent t-tests. Results: A majority of OB/GYNs report they "strongly recommend" seasonal influenza vaccination for their pregnant patients in the first (79%) or second and third trimesters (81%). Among those who do not strongly recommend the flu vaccine in the first trimester, many say this is because of their own concerns (28%) or their patients' concerns (44%) about safety. Older OB/GYNs, those in smaller practices, and those without academic affiliation were less likely to recommend the vaccine and more likely to have safety concerns. For example, 72% of those age 60+ strongly recommended the vaccine in the second and third trimester, compared with 86% of those ages 30-44 and 83% of those ages 45-59 (p < 0.05 for all comparisons). Conclusions: OB/GYNs across the country largely support seasonal flu vaccination among pregnant women. Nonetheless, safety is a concern for them and their patients. Outreach to support clinician decisions and conversations with pregnant patients may be most needed among older physicians, those in smaller practices, and those without academic affiliation.

Active SMS-based surveillance of adverse events following immunisation with influenza and pertussis-containing vaccines in Australian pregnant women using AusVaxSafety

BACKGROUND

Maternal immunisation is important to protect both mother and baby, but safety concerns can lead to low uptake. AusVaxSafety participant-based surveillance actively monitors adverse events following immunisation (AEFI) in Australia. We aimed to analyse AEFI in the days following vaccination with seasonal inactivated influenza vaccine (IIV) and/or reduced antigen diphtheria-tetanus-acellular pertussis vaccine (dTpa) in pregnant women in Australia.

METHODS

De-identified AEFI reports were solicited from vaccine recipients via automated SMS survey (using SmartVax software) following routine vaccination with IIV and/or dTpa at 219 national sentinel surveillance sites from 2015 to 2018. AEFI rates were compared by vaccine group (IIV alone, dTpa alone, or IIV and dTpa together), vaccine brand, trimester (IIV only) and vaccination period (April to August 2016-2018; IIV only). Women who had two vaccination encounters during surveillance were identified and AEFI rates compared for each dose.

RESULTS

Among 13,758 participants, overall AEFI rates were lower following IIV (4.9%) than dTpa (6.4%) or IIV and dTpa given concomitantly (7.4%). The AEFI profile was similar for both vaccines, with injection site reactions, tiredness, and headache most commonly reported. Injection site pain and swelling/redness were significantly more common in women who received dTpa than IIV. Reports of medical attendance following immunisation were similar (0.3%) for each vaccine group. AEFI rates did not differ by IIV brand (FluQuadri®, Fluarix® Tetra), dTpa brand (Boostrix®, Adacel®), or by trimester. Among women with sequential dTpa vaccinations, 6.0% (7/116) had an AEFI following their second dTpa dose.

CONCLUSIONS

Self-reported AEFI rates did not differ by trimester (IIV), or by vaccine brand (IIV or dTpa). Concomitant influenza and pertussis vaccination was associated with more frequent, but low rates of minor, expected AEFI. These real world 'citizen science-based' data provide further reassuring evidence of the safety of maternal vaccination.

Are all vaccines safe for the pregnant traveller? A systematic review and meta-analysis

Pregnant travellers and their offspring are vulnerable to severe outcomes following a wide range of infections. Vaccine-preventable diseases can have a particularly severe course in pregnant women, but little is known about the safety of travel vaccines in pregnant women. We performed a systematic review of all published literature concerning the safety of vaccines frequently given to travellers such as yellow fever, MMR (mumps, measles and rubella), influenza, Tdap (tetanus, diphtheria and pertussis), meningococcus, hepatitis A and B, rabies, polio, typhoid fever, tick-borne encephalitis and Japanese encephalitis vaccines. We included case series, cohort studies and randomized controlled trials (RCTs). For the meta-analysis, we included only RCTs that compared the administration of a vaccine to placebo or to no vaccine. Outcome measures included severe systemic adverse events, maternal outcomes related to the course of pregnancy, neonatal outcomes and local adverse events. We calculated the risk ratio and its 95% confidence interval as the summary measure. The safety of influenza vaccine is supported by high-quality evidence. For Tdap vaccine, no evidence of any harm was found in the meta-analysis of RCTs. A slight increase in chorioamnionitis rate was reported in 3 out of 12 observational studies. However, this small possible risk is far outweighed by a much larger benefit in terms of infant morbidity and mortality. Meningococcal vaccines are probably safe during pregnancy, as supported by RCTs comparing meningococcal vaccines to other vaccines. Data from observational studies support the safety of hepatitis A, hepatitis B and rabies vaccines, as well as that of the live attenuated yellow fever vaccine. We found little or no data about the safety of polio, typhoid, Japanese encephalitis, tick-borne encephalitis and MMR vaccines during pregnancy.

Precision immunization: a new trend in human vaccination

Vaccination has been one of the major revolutions in the history of human health. Vaccination programs have targeted entire populations such as infants or elderly subjects as a matter of being efficient with time and resources. These general populations are heterogeneous in terms of factors such as ethnicity, health status, and socio-economics. Thus, there have been variations in the safety and effectiveness profiles of certain vaccinations according to current population-wide strategies. As the concept of precision medicine has been raised in recent years, many researchers have suggested that vaccines could be administered more precisely in terms of particular target populations, vaccine formulations, regimens, and dosage levels. This review addresses the concept and framework of precision immunization, summarizes recent and representative clinical trials of among specific populations, mentions important factors to be addressed in customizing vaccinations, and provides suggestions on the establishment of precision immunization with the goal of maximizing the effectiveness of vaccines in general.

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.

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.

Predictors for influenza vaccination among Thai pregnant woman: The role of physicians in increasing vaccine uptake

BACKGROUND

Physician recommendation and attitudes and beliefs of pregnant women toward influenza and vaccination may influence vaccine uptake during pregnancy. We examined how physician recommendation and health beliefs of pregnant women may jointly affect influenza vaccination during pregnancy.

METHODS

Thai pregnant women aged ≥18 years and >13 gestational weeks attending antenatal care (ANC) clinics, and ANC physicians were recruited during May-August 2015. Women and physicians, linked using unique identifiers, provided data on demographic, health and work history, knowledge, attitudes, and beliefs toward influenza and vaccination, based on Health Belief Model constructs. Physicians also provided data on their practices in recommending influenza vaccination during pregnancy. Prevalence ratios for the association between knowledge, attitudes and beliefs of pregnant women, physician recommendation and documented receipt of vaccination within 30 days of the visit were calculated.

RESULTS

Among 610 women, the median age was 27 years; 266 (44%) and 344 (56%) were in the second and third trimesters, respectively. Twenty-one (3%) had pre-existing conditions. Of 60 physicians with the median years of practice of 5; 17 (28%) reported frequently/usually/always recommending influenza vaccine to their pregnant patients, while 43 (72%) reported never/rarely/sometimes recommending the vaccine. Controlling for the pregnant women's knowledge and beliefs, pregnant women whose physician recommended influenza vaccination were 2.3 times (95% confidence interval 1.4-3.8) more likely to get vaccinated.

CONCLUSIONS

In this study, physician recommendation was the only significant factor associated with influenza vaccine uptake among Thai pregnant women. Understanding physicians' motivation/barrier to recommending influenza vaccination to pregnant women may increase coverage.

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.

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.

Safety, equity and monitoring: a review of the gaps in maternal vaccination strategies for Aboriginal and Torres Strait Islander women

Influenza and pertussis infections are disproportionately higher among Aboriginal and Torres Strait Islander women and their infants compared to other Australians. These infections are potentially preventable through vaccination in pregnancy; however, there is a lack of systematic monitoring and therefore knowledge of vaccine uptake, safety and effectiveness in Australia, and specifically among Aboriginal and Torres Strait Islander women. The limited data available suggest there is a lower uptake of maternal vaccination among Aboriginal and Torres Strait Islander women compared to non-Aboriginal and Torres Strait Islander women, and this review seeks to explore potential reasons and the knowledge gaps in this regard. Other key gaps include the equitable access to quality antenatal care for Aboriginal and Torres Strait Islander women; and pregnancy loss <20 weeks gestation. Furthermore, our review highlights the importance of addressing these gaps in maternal vaccination strategies in partnership with Aboriginal and Torres Strait Islander peoples.

Optimal timing of influenza vaccine during pregnancy: A systematic review and meta-analysis

BACKGROUND

Pregnant women have an elevated risk of illness and hospitalisation from influenza. Pregnant women are recommended to be prioritised for influenza vaccination during any stage of pregnancy. The risk of seasonal influenza varies substantially throughout the year in temperate climates; however, there is limited knowledge of how vaccination timing during pregnancy impacts the benefits received by the mother and foetus.

OBJECTIVES

To compare antenatal vaccination timing with regard to influenza vaccine immunogenicity during pregnancy and transplacental transfer to their newborns.

METHODS

Studies were eligible for inclusion if immunogenicity to influenza vaccine was evaluated in women stratified by trimester of pregnancy. Haemagglutination inhibition (HI) titres, stratified by trimester of vaccination, had to be measured at either pre-vaccination and within one month post-vaccination, post-vaccination and at delivery in the mother, or in cord/newborn blood. Authors searched PubMed, Scopus, Web of Science and EMBASE databases from inception until June 2016 and authors of identified studies were contacted for additional data. Extracted data were tabulated and summarised via random-effect meta-analyses and qualitative methods.

RESULTS

Sixteen studies met the inclusion criteria. Meta-analyses found that compared with women vaccinated in an earlier trimester, those vaccinated in a later trimester had a greater fold increase in HI titres (1.33- to 1.96-fold) and higher HI titres in cord/newborn blood (1.21- to 1.64-fold).

CONCLUSIONS

This review provides comparative analysis of the effect of vaccination timing on maternal immunogenicity and protection of the infant that is informative and relevant to current vaccine scheduling for pregnant women.

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 Among Pregnant Women in the United States: Findings from the 2012-2016 National Health Interview Survey

Background: The issue of suboptimal influenza vaccination coverage among pregnant women remains relevant. Our study aimed to explore the determinants and coverage of influenza vaccination among pregnant women in the United States using a nationally representative sample. Materials and Methods: This study was conducted with the 2012-2016 U.S. National Health Interview Survey. The Andersen's Health Behavior Model was applied as the conceptual framework to explore potential factors that may influence the influenza vaccination rate. A series of individual determinants, categorized into predisposing, enabling, and need factors, were compared using logistic regressions between women who received an influenza vaccination before or during pregnancy and those who did not. Results: An average of 36% women received an influenza vaccination before or during pregnancy among an estimated five million pregnant women. Even though the percentage increased from 31% in 2012 to 40% in 2016, it remained lower than the Healthy People 2020 target of 80%. The odds of receiving an influenza vaccination before or during pregnancy were lower among women who had public or no insurance coverage (odds ratio [OR]; 95% confidence interval, 0.510 [0.323-0.806] and 0.351 [0.175-0.705], respectively), lived in South (0.546 [0.336-0.887]), ever smoked 100 cigarettes (0.622 [0.419-0.923]), and had infrequent to light alcohol consumption in the past year (0.670 [0.457-0.983], reference: no alcohol consumption in the past year). Having a bachelor's degree increased the odds of getting an influenza vaccine compared to a high school diploma or less (2.086 [1.353-3.215]). Conclusions: Our study found that the influenza vaccination coverage among pregnant women remains suboptimal, and disparities may still exist across women with different sociodemographic and socioeconomic status. Clinicians should actively recommend influenza vaccination for pregnant women, and policy makers may consider developing interventions to improve the vaccination rate.

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.

Patient attitudes toward influenza and tetanus, diphtheria and acellular pertussis vaccination in pregnancy

BACKGROUND

Routine influenza and tetanus, diphtheria and acellular pertussis (Tdap) vaccination of pregnant women to prevent poor maternal, fetal and neonatal outcomes is recommended practice; however, actual rates of influenza vaccine acceptance are typically well below the (Healthy People 2020, 2015) goal of 80%.

OBJECTIVE

We sought to identify barriers to accepting either vaccination.

MATERIALS AND METHODS

From December 2014 to April 2015 women were given a questionnaire eliciting their experiences, attitudes and history of influenza and Tdap vaccination in pregnancy during their routine prenatal care appointments at a tertiary care center. Patient demographics were included in the questionnaire. A similar questionnaire was administered to prenatal care providers. Patient influenza and Tdap vaccination acceptance rates were compared and predictors of vaccine acceptance were analyzed with bivariate logistic regression.

RESULTS

Out of the 400 patient questionnaires distributed, 338 (84.5%) were completed and returned; 24 of 45 (53.3%) provider questionnaires were returned. Vaccination acceptance rates were 70.7% for the influenza vaccine and 76.3% for the Tdap vaccine. The logistic regression model indicated that predictors of acceptance for either vaccine in pregnancy are patient attitude and previous vaccination history. Patient attitudes were more favorable towards Tdap than influenza vaccination. The combination of healthcare provider recommendation and educational materials was significantly predictive of both Tdap and influenza vaccine acceptance. The most common reasons given for declining the influenza vaccine were safety concerns; the most common reasons given for declining the Tdap vaccine were that patients did not think it was required again when they received the vaccine before pregnancy.

CONCLUSIONS

Our study suggests that providers can improve Tdap and influenza vaccination acceptance in pregnancy by recommending the vaccination in combination with provision of educational materials on the vaccines.

Vaccines for preventing influenza in healthy adults

BACKGROUND

The consequences of influenza in adults are mainly time off work. Vaccination of pregnant women is recommended internationally. This is an update of a review published in 2014. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated due to their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 12), MEDLINE (January 1966 to 31 December 2016), Embase (1990 to 31 December 2016), the WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017), and ClinicalTrials.gov (1 July 2017), as well as checking the bibliographies of retrieved articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy individuals aged 16 to 65 years. Previous versions of this review included observational comparative studies assessing serious and rare harms cohort and case-control studies. Due to the uncertain quality of observational (i.e. non-randomised) studies and their lack of influence on the review conclusions, we decided to update only randomised evidence. The searches for observational comparative studies are no longer updated.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We rated certainty of evidence for key outcomes (influenza, influenza-like illness (ILI), hospitalisation, and adverse effects) using GRADE.

MAIN RESULTS

We included 52 clinical trials of over 80,000 people assessing the safety and effectiveness of influenza vaccines. We have presented findings from 25 studies comparing inactivated parenteral influenza vaccine against placebo or do-nothing control groups as the most relevant to decision-making. The studies were conducted over single influenza seasons in North America, South America, and Europe between 1969 and 2009. We did not consider studies at high risk of bias to influence the results of our outcomes except for hospitalisation.Inactivated influenza vaccines probably reduce influenza in healthy adults from 2.3% without vaccination to 0.9% (risk ratio (RR) 0.41, 95% confidence interval (CI) 0.36 to 0.47; 71,221 participants; moderate-certainty evidence), and they probably reduce ILI from 21.5% to 18.1% (RR 0.84, 95% CI 0.75 to 0.95; 25,795 participants; moderate-certainty evidence; 71 healthy adults need to be vaccinated to prevent one of them experiencing influenza, and 29 healthy adults need to be vaccinated to prevent one of them experiencing an ILI). The difference between the two number needed to vaccinate (NNV) values depends on the different incidence of ILI and confirmed influenza among the study populations. Vaccination may lead to a small reduction in the risk of hospitalisation in healthy adults, from 14.7% to 14.1%, but the CI is wide and does not rule out a large benefit (RR 0.96, 95% CI 0.85 to 1.08; 11,924 participants; low-certainty evidence). Vaccines may lead to little or no small reduction in days off work (-0.04 days, 95% CI -0.14 days to 0.06; low-certainty evidence). Inactivated vaccines cause an increase in fever from 1.5% to 2.3%.We identified one RCT and one controlled clinical trial assessing the effects of vaccination in pregnant women. The efficacy of inactivated vaccine containing pH1N1 against influenza was 50% (95% CI 14% to 71%) in mothers (NNV 55), and 49% (95% CI 12% to 70%) in infants up to 24 weeks (NNV 56). No data were available on efficacy against seasonal influenza during pregnancy. Evidence from observational studies showed effectiveness of influenza vaccines against ILI in pregnant women to be 24% (95% CI 11% to 36%, NNV 94), and against influenza in newborns from vaccinated women to be 41% (95% CI 6% to 63%, NNV 27).Live aerosol vaccines have an overall effectiveness corresponding to an NNV of 46. The performance of one- or two-dose whole-virion 1968 to 1969 pandemic vaccines was higher (NNV 16) against ILI and (NNV 35) against influenza. There was limited impact on hospitalisations in the 1968 to 1969 pandemic (NNV 94). The administration of both seasonal and 2009 pandemic vaccines during pregnancy had no significant effect on abortion or neonatal death, but this was based on observational data sets.

AUTHORS' CONCLUSIONS

Healthy adults who receive inactivated parenteral influenza vaccine rather than no vaccine probably experience less influenza, from just over 2% to just under 1% (moderate-certainty evidence). They also probably experience less ILI following vaccination, but the degree of benefit when expressed in absolute terms varied across different settings. Variation in protection against ILI may be due in part to inconsistent symptom classification. Certainty of evidence for the small reductions in hospitalisations and time off work is low. Protection against influenza and ILI in mothers and newborns was smaller than the effects seen in other populations considered in this review.Vaccines increase the risk of a number of adverse events, including a small increase in fever, but rates of nausea and vomiting are uncertain. The protective effect of vaccination in pregnant women and newborns is also very modest. We did not find any evidence of an association between influenza vaccination and serious adverse events in the comparative studies considered in this review. Fifteen included RCTs were industry funded (29%).

Effects of prior influenza virus vaccination on maternal antibody responses: Implications for achieving protection in the newborns

BACKGROUND

In the US, influenza vaccination is recommended annually to everyone ≥6months. Prior receipt of influenza vaccine can dampen antibody responses to subsequent vaccination. This may have implications for pregnant women and their newborns, groups at high risk for complications from influenza infection.

OBJECTIVE

This study examined effects of prior vaccination on maternal and cord blood antibody levels in a cohort of pregnant women in the US.

STUDY DESIGN

Influenza antibody titers were measured in 141 pregnant women via the hemagglutination inhibition (HAI) assay prior to receipt of quadrivalent influenza vaccine, 30days post-vaccination, and at delivery (maternal and cord blood). Logistic regression analyses adjusting for age, BMI, parity, gestational age at vaccination, and year of vaccination compared HAI titers, seroprotection, and seroconversion in women with versus without vaccination in the prior year.

RESULTS

Compared to those without vaccination in the previous year (n=50), women with prior vaccination (n=91) exhibited higher baseline antibody titers and/or seroprotection rates against all four strains after controlling for covariates. Prior vaccination also predicted lower antibody responses and seroconversion rates at one month post-vaccination. However, at delivery, there were no significant differences in antibody titers or seroprotection rates in women or newborns, and no meaningful differences in the efficiency of antibody transfer, as indicated by the ratio of cord blood to maternal antibody titers at the time of delivery.

CONCLUSION

In this cohort of pregnant women, receipt of influenza vaccine the previous year predicted higher baseline antibody titers and decreased antibody responses at one month post-vaccination against all influenza strains. However, prior maternal vaccination did not significantly affect either maternal antibody levels at delivery or antibody levels transferred to the neonate. This study is registered with the NIH as a clinical trial (NCT02148874).

Association of influenza vaccination during pregnancy with birth outcomes in Nicaragua

Background: Studies have shown that influenza vaccination during pregnancy reduces the risk of influenza disease in pregnant women and their offspring. Some have proposed that maternal vaccination may also have beneficial effects on birth outcomes. In 2014, we conducted an observational study to test this hypothesis using data from two large hospitals in Managua, Nicaragua.

Methods: We conducted a retrospective cohort study to evaluate associations between influenza vaccination and birth outcomes. We carried out interviews and reviewed medical records post-partum to collect data on demographics, influenza vaccination during pregnancy, birth outcomes and other risk factors associated with adverse neonatal outcomes. We used influenza surveillance data to adjust for timing of influenza circulation. We assessed self-reports of influenza vaccination status by further reviewing medical records of those who self-reported but did not have readily available evidence of vaccination status. We performed multiple logistic regression (MLR) and propensity score matching (PSM).

Results: A total of 3268 women were included in the final analysis. Of these, 55% had received influenza vaccination in 2014. Overall, we did not observe statistically significant associations between influenza vaccination and birth outcomes after adjusting for risk factors, with either MLR or PSM. With PSM, after adjusting for risk factors, we observed protective associations between influenza vaccination in the second and third trimester and preterm birth (aOR: 0.87; 95% confidence interval (CI): 0.75–0.99 and aOR: 0.66; 95% CI: 0.45–0.96, respectively) and between influenza vaccination in the second trimester and low birth weight (aOR: 0.80; 95% CI: 0.64–0.97).

Conclusions: We found evidence to support an association between influenza vaccination and birth outcomes by trimester of receipt with data from an urban population in Nicaragua. The study had significant selection and recall biases. Prospective studies are needed to minimize these biases.

Redirecting reproductive immunology research toward pregnancy as a period of temporary immune tolerance

Referring to two recent publications, we here propose that clinical reproductive immunology has for decades stagnated because reproductive medicine, including assisted reproduction (AR), has failed to accept embryo implantation as an immune system-driven process, dependent on establishment of maternal tolerance toward the implanting fetal semi-allograft (and complete allograft in cases of oocyte donation). Pregnancy represents a biologically unique period of temporary (to the period of gestation restricted) tolerance, otherwise only known in association with parasitic infections. Rather than investigating the immune pathways necessary to induce this rather unique state of tolerance toward the rapidly growing parasitic antigen load of the fetus, the field, instead, concentrated on irrelevant secondary immune phenomena (i.e., "immunological noise"). It, therefore, does not surprise that interesting recent research, offering new potential insights into maternal tolerance during pregnancy, was mostly published outside of the field of reproductive medicine. This research offers evidence for existence of inducible maternal tolerance pathways with the ability of improving maternal fecundity and, potentially, reducing such late pregnancy complications as premature labor and preeclampsia/eclampsia due to premature abatement of maternal tolerance. Increasing evidence also suggests that tolerance-inducing immune pathways are similar in successful pregnancy, successful organ transplantation and, likely also in the tolerance of "self" (i.e., prevention of autoimmunity). Identifying and isolating these pathways, therefore, may greatly benefit all three of these clinical areas, and research in reproductive immunology should be accordingly redirected.

Birth outcomes for Australian mother-infant pairs who received an influenza vaccine during pregnancy, 2012-2014: The FluMum study

INTRODUCTION

In Australia, influenza vaccination is recommended for all women who will be pregnant during the influenza season. Vaccine safety and effectiveness are key concerns and influencers of uptake for both vaccine providers and families. We assessed the safety of receiving an influenza vaccination during any trimester of pregnancy with respect to preterm births and infant birthweight.

METHODS

We conducted a nested retrospective cohort study of 'FluMum' participants (2012-2014). Our primary exposure of interest was influenza vaccination during pregnancy. The primary outcomes of interest were infant birthweight and weeks' gestation at birth for live singleton infants. Analyses included comparisons of these birth outcomes by vaccination status and trimester of pregnancy an influenza vaccine was given. We calculated means, proportions, and relative risks and performed multivariable logistic regression for potential confounding factors.

RESULTS

In the 7126 mother-infant pairs enrolled in this study, mean maternal age at infant birth was 31.7years. Influenza vaccine uptake in pregnancy was 34%. Most mothers with a known date of vaccination received a vaccine in the second trimester (51%). Those mothers with a co-morbidity or risk factor were 13% more likely to have influenza vaccine during pregnancy compared to other mothers (RR 1.13, 95% CI 1.04-1.24, p=0.007). Mean weeks' gestation at birth was 38.7 for the vaccinated and 38.8 for the unvaccinated group (p=0.051). Infants in the vaccinated group weighed 15g less in birthweight compared to the unvaccinated infants (95% CI -12.8 to 42.2, p=0.29).

CONCLUSION

Results arising from this large Australian cohort study are reassuring with respect to two critical safety outcomes; preterm births and low infant birthweights. Studies examining a broader range of birth outcomes following influenza vaccination during pregnancy are required, particularly now that maternal vaccination in pregnancy has expanded to include pertussis as well as influenza.

[Implementation of seasonal influenza and human papillomavirus vaccination recommendations in gynecological practices in Germany]

In Germany, seasonal influenza vaccination has been recommended for pregnant women since 2010 and human papillomavirus (HPV) vaccination for girls since 2007. Gynecologists play an important role in the communication and vaccination of these two target groups. Moreover, seasonal influenza vaccination is also recommended for healthcare workers, as well as adults aged ≥ 60 years and individuals with underlying chronic diseases. The aim of this study was to gain first insights into the acceptance and implementation of the seasonal influenza und HPV vaccination recommendations in gynecological practices. In the context of the national influenza immunization campaign-which is jointly carried out by the Robert Koch Institute (RKI) and the Federal Centre for Health Education (BZgA)-a questionnaire was sent together with influenza information kits to 7477 gynecologists in September 2014. Data from 1469 (20 %) gynecologists were included in the analysis. 72 % of respondents reported that they themselves received a seasonal influenza shot each year. The majority of gynecologists recommended seasonal influenza vaccination for pregnant women (93 %) and HPV vaccination for girls (97 %). The most commonly stated reasons against influenza vaccination were safety concerns. Those against HPV vaccination were effectiveness concerns. Additionally, for both vaccinations the provision of vaccine-related information to the patient was considered too time consuming.The high acceptance of seasonal influenza and HPV vaccination among gynecologists is discordant with the available vaccination coverage figures in Germany. Gynecologists must be reminded of their important role in the prevention of vaccine-preventable diseases in adolescents and adult women. Immunization and communication skills should be considered more strongly as an integral part of medical education and further training for gynecologists.

Risk for Congenital Malformation With H1N1 Influenza Vaccine: A Cohort Study With Sibling Analysis

BACKGROUND

Earlier studies reporting varying risk estimates for congenital malformation in offspring of mothers undergoing vaccination against H1N1 influenza during pregnancy did not consider the potential role of confounding by familial (genetic and shared environmental) factors.

OBJECTIVE

To evaluate an association between maternal H1N1 vaccination during pregnancy and offspring malformation, with familial factors taken into account.

DESIGN

Population-based prospective study.

SETTING

Sweden.

PARTICIPANTS

Liveborn offspring born between 1 October 2009 and 1 October 2011 to mothers receiving monovalent AS03-adjuvanted H1N1 influenza vaccine (Pandemrix [GlaxoSmithKline]) during pregnancy. A total of 40 983 offspring were prenatally exposed to the vaccine, 14 385 were exposed within the first trimester (14 weeks), and 7502 were exposed during the first 8 weeks of pregnancy. Exposed offspring were compared with 197 588 unexposed offspring. Corresponding risks in exposed versus unexposed siblings were also estimated.

MEASUREMENTS

Congenital malformation, with subanalyses for congenital heart disease, oral cleft, and limb deficiency.

RESULTS

Congenital malformation was observed in 2037 (4.97%) exposed offspring and 9443 (4.78%) unexposed offspring. Adjusted risk for congenital malformation was 4.98% in exposed offspring versus 4.96% in unexposed offspring (risk difference, 0.02% [95% CI, -0.26% to 0.30%]). The corresponding risk differences were 0.16% (CI, -0.23% to 0.56%) for vaccination during the first trimester and 0.10% (CI, -0.41% to 0.62%) for vaccination in the first 8 weeks. Using siblings as comparators yielded no statistically significant risk differences.

LIMITATIONS

The study was based on live births, and the possibility that data on miscarriage or induced abortion could have influenced the findings cannot be ruled out. Study power was limited in analyses of specific malformations.

CONCLUSION

When intrafamilial factors were taken into consideration, H1N1 vaccination during pregnancy did not seem to be linked to overall congenital malformation in offspring, although risk increases for specific malformations could not be ruled out completely.

PRIMARY FUNDING SOURCE

Swedish Research Council and Swedish Council for Working Life and Social Research.

Use of existing systematic reviews for evidence assessments in infectious disease prevention: a comparative case study

BACKGROUND

Given limited resources and time constraints, the use of existing systematic reviews (SR) for the development of evidence-based public health recommendations has become increasingly important. Recently, a five-step approach for identifying, analyzing, appraising and using existing SRs based on recent guidance by the US Agency for Healthcare Research and Quality (AHRQ) was proposed within the Project on a Framework for Rating Evidence in Public Health (PRECEPT). However, case studies are needed to test whether this approach is useful, what challenges arise and how problems can be solved.

METHODS

In two case studies, the five-step approach was applied to integrate existing SRs in the development of evidence-based public health recommendations. Case study A focused on the role of neonatal sepsis as a risk factor for adverse neurodevelopmental outcome. Case study B examined the efficacy, effectiveness and safety of influenza vaccination during pregnancy. For each step, we report the approach of the review team, discuss challenges and describe solutions.

RESULTS

For case study A, one existing SR was identified, while in case study B four SRs were eligible for analysis. We found that comparison of inclusion criteria alone was sufficient to judge on relevance of SRs in case study A, but not B. Although methodological quality of all identified SRs was acceptable, risk of bias assessments of individual studies included in the SRs had to be repeated in both case studies. Particular challenges appeared in case study B where multiple SRs addressed the same research question. With the help of spreadsheets comparing the characteristics of the existing SR we decided to use the most comprehensive one for our evidence synthesis and supplemented the results with those from the other SRs.

CONCLUSIONS

In both case studies using the complete SR was not possible. The five-step approach provided useful and structured guidance and should be routinely applied when using existing SRs as a basis for evidence-based recommendations in public health. In situations where more than one SR has to be considered, the development of spreadsheets comparing characteristics, inclusion criteria, risk of bias, included studies and outcomes seems useful.

Prevention and Control of Seasonal Influenza with Vaccines

This report updates the 2015-16 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines (Grohskopf LA, Sokolow LZ, Olsen SJ, Bresee JS, Broder KR, Karron RA. Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices, United States, 2015-16 influenza season. MMWR Morb Mortal Wkly Rep 2015;64:818-25). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For the 2016-17 influenza season, inactivated influenza vaccines (IIVs) will be available in both trivalent (IIV3) and quadrivalent (IIV4) formulations. Recombinant influenza vaccine (RIV) will be available in a trivalent formulation (RIV3). In light of concerns regarding low effectiveness against influenza A(H1N1)pdm09 in the United States during the 2013-14 and 2015-16 seasons, for the 2016-17 season, ACIP makes the interim recommendation that live attenuated influenza vaccine (LAIV4) should not be used. Vaccine virus strains included in the 2016-17 U.S. trivalent influenza vaccines will be an A/California/7/2009 (H1N1)-like virus, an A/Hong Kong/4801/2014 (H3N2)-like virus, and a B/Brisbane/60/2008-like virus (Victoria lineage). Quadrivalent vaccines will include an additional influenza B virus strain, a B/Phuket/3073/2013-like virus (Yamagata lineage).Recommendations for use of different vaccine types and specific populations are discussed. A licensed, age-appropriate vaccine should be used. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended product is otherwise appropriate. This information is intended for vaccination providers, immunization program personnel, and public health personnel. Information in this report reflects discussions during public meetings of ACIP held on October 21, 2015; February 24, 2016; and June 22, 2016. These recommendations apply to all licensed influenza vaccines used within Food and Drug Administration-licensed indications, including those licensed after the publication date of this report. Updates and other information are available at CDC's influenza website (http://www.cdc.gov/flu). Vaccination and health care providers should check CDC's influenza website periodically for additional information.

The safety of maternal immunization

Maternal vaccination offers the opportunity to protect pregnant women and their infants against potentially serious disease. As both pregnant women and their newborns are vulnerable to severe illness, the potential public health impact of mass maternal vaccination programs is remarkable. Several high-income countries recommend seasonal influenza and acellular pertussis vaccines, and many developing countries recommend immunization against tetanus during pregnancy. There is a significant amount of literature supporting the safety of vaccination during pregnancy. As other vaccines are newly introduced for pregnant women, routine systems for monitoring vaccine safety in pregnant women are needed. To facilitate meta-analyses and comparison across systems and studies, future research and surveillance initiatives should utilize the same criteria for defining adverse events following immunization among pregnant women. At least 2 areas require further exploration: 1) identification of pregnancy outcomes associated with concomitant and closely spaced vaccines; 2) evaluation of possible improvement in birth outcomes associated with maternal vaccination. Given the public health impact of maternal vaccination, the existing evidence supporting the safety of vaccination during pregnancy should be used to reassure pregnant women and their providers and improve vaccine uptake in pregnancy.