Effectiveness of seasonal trivalent influenza vaccination against hospital-attended acute respiratory infections in pregnant women: A retrospective cohort study

Influenza in Pregnancy: Prevention and Treatment: ACOG Committee Statement No. 7

Pregnant and postpartum individuals are at significantly higher risk of serious complications related to seasonal and pandemic influenza infections compared with nonpregnant people. The Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists (ACOG) recommend that all adults receive an annual influenza vaccine and that individuals who are or will be pregnant during influenza season receive an inactivated or recombinant influenza vaccine as soon as it is available. Although the influenza vaccine significantly lowers the risk of severe disease, it will not prevent all infections. Obstetrician-gynecologists and other obstetric health care professionals should consider both influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection for pregnant individuals who present with symptoms of respiratory illness. Antiviral treatment should not be delayed while awaiting respiratory infection test results, and a patient's vaccination status should not affect the decision to treat. Obstetrician-gynecologists and other obstetric care professionals can help reduce disparities in influenza vaccination rates as well as severe outcomes related to influenza infection by strongly recommending influenza vaccination to all patients.

Factors Associated With Influenza Vaccination During Pregnancy: A Real-World Evidence-Based Study

Pregnant women are at increased risk of influenza-related complications. However, the rate of influenza vaccination among pregnant women in Taiwan is low. By analyzing real-world data in this study, we investigated the factors associated with influenza vaccination during pregnancy in Taiwan. This study was a cross-sectional study. We collected real-world data from 2 databases in Taiwan: the Birth Certificate Database and the National Health Insurance Research Database. The study population was pregnant between October 2014 and December 2016 in Taiwan. The multivariate logistic regression was performed to identify factors associated with influenza vaccination, including maternal sociodemographics, trimester, comorbidities, and health-care utilization. The vaccination rate of among pregnant women was 8.2%. Factors significantly associated with a high likelihood of influenza vaccination were age between 30 and 34 years (odds ratio [OR]: 1.14; 95% confidence interval [CI]: 1.10-1.19), second trimester (OR: 1.80; 95% CI: 1.75-1.85), income equal to or exceeding NT$ 38 201 (OR: 1.92; 95% CI: 1.86-1.99), hypertension (OR: 1.16; 95% CI: 1.05-1.29), cardiovascular disease (OR: 1.29; 95% CI: 1.17-1.42), autoimmune disease (OR: 1.47; 95% CI: 1.38-1.58), and chronic pulmonary disease (OR: 1.24; 95% CI: 1.18-1.31). A low level of urbanization, at least 1 hospitalization in the previous year, and the presence of pregnancy complications (eg, gestational diabetes, preeclampsia, and placenta previa) were associated with a lower likelihood rate of influenza vaccination. The influenza vaccination rate among pregnant women in Taiwan was low. Age, gestational age, income level, urbanization level, hypertension, cardiovascular disease, autoimmune disease, chronic pulmonary disease, and pregnancy complications may be associated with influenza vaccination among pregnant women.

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.

Impact of Obesity and Diabetes in Pregnant Women on Their Immunity and Vaccination

Pregnant women with obesity and diabetes are at increased risk of developing infections and other complications during pregnancy. Several mechanisms are involved in the immunological mechanisms that contribute to reduced immunity in these populations. Both obesity and diabetes are associated with chronic low-grade inflammation that can lead to an overactive immune response. Pregnant women with obesity and diabetes often have an increase in pro-inflammatory cytokines and adipokines, such as TNF-α, IL-6, IL-1β, leptin, and resistin, which are involved in the inflammatory response. Insulin resistance can also affect the functioning of immune cells. Furthermore, both conditions alter the composition of the gut microbiome, which produces a variety of biomolecules, including short-chain fatty acids, lipopolysaccharides, and other metabolites. These substances may contribute to immune dysfunction. In addition to increasing the risk of infections, obesity and diabetes can also affect the efficacy of vaccinations in pregnant women. Pregnant women with obesity and diabetes are at increased risk of developing severe illness and complications from COVID-19, but COVID-19 vaccination may help protect them and their fetuses from infection and its associated risks. Since both obesity and diabetes classify a pregnancy as high risk, it is important to elucidate the impact of these diseases on immunity and vaccination during pregnancy. Research examining the efficacy of the COVID-19 vaccine in a high-risk pregnant population should be of particular value to obstetricians whose patients are hesitant to vaccinate during pregnancy. Further research is needed to better understand these mechanisms and to develop effective interventions to improve immune function in these populations.

Rates of Influenza and Tdap Vaccination in Teaching and Private Obstetrical Practices, and the Influence of Vaccine Hesitancy

OBJECTIVES

We evaluated differences in vaccination rates of patients of teaching and private practices, and explored the rate of vaccine hesitancy in pregnant women.

METHODS

This was a cross-sectional study of a convenience sample of recently delivered women. Women completed a survey, which included a question about whether they received the influenza and/or Tdap vaccine, and a vaccine hesitancy scale for both influenza and Tdap vaccines. We also reviewed prenatal records to confirm vaccine administration and collected demographic data. Patients who received care on the teaching service (care by residents supervised by faculty) were compared with those who received care from 26 private practitioners in nine groups. The primary outcome was rate of vaccination. Fisher's exact test was performed to compare groups.

RESULTS

Of the 231 women approached, 208 (90.0%) agreed to participate. Of the 208 participants, 70 (33.7%) had prenatal care with a teaching practice, and 138 (66.3%) with a private practice. Patients of teaching practices had a higher influenza and Tdap vaccination rate compared with patients of private practices (Influenza: 70% versus 54.3%, p = 0.036; Tdap: 77.1% versus 58.4%, p = 0.009). Among the entire cohort, 55.3% had some degree of vaccine hesitancy. This did not differ between teaching and private practices (54.3% versus 55.8%, p = 0.883).

CONCLUSIONS

In spite of similar prevalence of vaccine hesitancy, pregnant women cared for in teaching practices had higher vaccination rates than those cared for in private practices.

The association between maternal influenza vaccination during pregnancy and adverse birth outcomes in the United States: Pregnancy risk Assessment Monitoring System (PRAMS)

OBJECTIVE

Influenza vaccination during pregnancy is highly recommended. We examined the association between maternal influenza vaccination and adverse birth outcomes.

METHODS

This cross-sectional study used data from the Pregnancy Risk Assessment Monitoring System (PRAMS) during 2012-2017. The primary exposure was the receipt of influenza vaccination during pregnancy. Low birth weight (LBW), preterm birth (PTB), and small for gestational age (SGA) were the primary outcomes. We conducted multivariable logistic regression models to estimate the adjusted odds ratios (AOR) and 95% confidence intervals (CI). Covariates used to adjust confounding included maternal age, marital status, education, race and ethnicity, insurance status before pregnancy, and smoking status. For a subgroup in 2012-2015, we analyzed the association between influenza vaccination in each trimester and adverse birth outcomes.

RESULTS

During 2012-2017, compared with unvaccinated women, women vaccinated during pregnancy had a lower risk of LBW and PTB. During 2012-2015, maternal influenza vaccination in the 1st and 3rd trimesters was associated with a reduced risk of LBW and PTB, and vaccination in the 3rd trimester had a greater protective effect than in the 1st trimester. Influenza vaccination was not associated with SGA regardless of trimester.

CONCLUSIONS

Our findings suggest that influenza vaccination during pregnancy is a safe and effective way to protect newborns.

Usefulness of linked data for infectious disease events: a systematic review

Surveillance is a key public health function to enable early detection of infectious disease events and inform public health action. Data linkage may improve the depth of data for response to infectious disease events. This study aimed to describe the uses of linked data for infectious disease events. A systematic review was conducted using Pubmed, CINAHL and Web of Science. Studies were included if they used data linkage for an acute infectious disease event (e.g. outbreak of disease). We summarised the event, study aims and designs; data sets; linkage methods; outcomes reported; and benefits and limitations. Fifty-four studies were included. Uses of linkage for infectious disease events included assessment of severity of disease and risk factors; improved case finding and contact tracing; and vaccine uptake, safety and effectiveness. The ability to conduct larger scale population level studies was identified as a benefit, in particular for rarer exposures, risk factors or outcomes. Limitations included timeliness, data quality and inability to collect additional variables. This review demonstrated multiple uses of data linkage for infectious disease events. As infectious disease events occur without warning, there is a need to establish pre-approved protocols and the infrastructure for data-linkage to enhance information available during an event.

Longitudinal, population-based cohort study of prenatal influenza vaccination and influenza infection in childhood

BACKGROUND

Influenza vaccination is recommended to protect mothers and their infants from influenza infection. Few studies have evaluated the health impacts of in utero exposure to influenza vaccine among children more than six months of age.

METHODS

We used probabilistically linked administrative health records to establish a mother-child cohort to evaluate the risk of influenza and acute respiratory infections associated with maternal influenza vaccination. Outcomes were laboratory-confirmed influenza (LCI) and hospitalization for influenza or acute respiratory infection (ARI). Adjusted hazard ratios (aHRs) accounted for child's Aboriginal status and were weighted by the inverse-probability of treatment.

RESULTS

14,396 (11.5%) children were born to vaccinated mothers. Maternally vaccinated infants aged < 6 months had lower risk of LCI (aHR: 0.33; 95% CI: 0.13, 0.85), influenza-associated hospitalization (aHR: 0.39; 95% CI: 0.16, 0.94) and ARI-associated hospitalization (aHR: 0.85; 95% CI: 0.77, 0.94) compared to maternally unvaccinated infants. With the exception of an increased risk of LCI among children aged 6 months to < 2 years old following first trimester vaccination (aHR: 2.28; 95% CI: 1.41, 3.69), there were no other differences in the risk of LCI, influenza-associated hospitalization or ARI-associated hospitalization among children aged > 6 months.

CONCLUSION

Study results show that maternal influenza vaccination is effective in preventing influenza in the first six months and had no impact on respiratory infections after two years of age.

Association between a usual source of care and influenza vaccination rates among pregnant women

PURPOSE

Pregnant women and infants less than 6 months of age have a higher risk of complications from influenza. Vaccination is recommended for pregnant women to decrease risk of infection and hospitalizations between both the women themselves and infants. However, vaccination rates remain low in pregnant women. The objective of this study was to determine the association between having a usual source of care and seasonal influenza vaccination rates among women who were pregnant between 2012 and 2016.

METHODS

A retrospective study was conducted using pooled data from the 2012-2016 Medical Expenditure Panel Survey. Frequencies of seasonal influenza vaccinations and other sociodemographic factors were estimated. A multivariable log-binomial regression model was used to examine the association between having a usual source of care and seasonal influenza vaccination rates.

RESULTS

The weighted influenza vaccination rate among pregnant women was 54.5%. About one third did not have a usual source of care. The adjusted prevalence ratio of receiving an influenza vaccine for pregnant women without a usual source of care was 0.76 (95% confidence interval = 0.60-0.98). The top three main reasons for not having a usual source of care were being seldom or never sick (55.7%), not having health insurance (10.6%), and having recently moved to an area (9.9%).

CONCLUSIONS

Pregnant women without a usual source of care had significantly lower probability of being vaccinated against seasonal influenza. Improving access to care through greater insurance coverage, addressing cost barriers, and providing patient education may help improve vaccination rates in this population.

Safety, Immunogenicity, Efficacy and Effectiveness of Inactivated Influenza Vaccines in Healthy Pregnant Women and Children Under 5 Years: An Evidence-Based Clinical Review

Annual influenza vaccination is often recommended for pregnant women and young children to reduce the risk of severe influenza. However, most studies investigating the safety, immunogenicity, and efficacy or effectiveness of influenza vaccines are conducted in healthy adults. In this evidence-based clinical review, we provide an update on the safety profile, immunogenicity, and efficacy/effectiveness of inactivated influenza vaccines (IIVs) in healthy pregnant women and children <5 years old. Six electronic databases were searched until May 27, 2021. We identified 3,731 articles, of which 93 met the eligibility criteria and were included. The IIVs were generally well tolerated in pregnant women and young children, with low frequencies of adverse events following IIV administration; however, continuous vaccine safety monitoring systems are necessary to detect rare adverse events. IIVs generated good antibody responses, and the seroprotection rates after IIVs were moderate to high in pregnant women (range = 65%-96%) and young children (range = 50%-100%), varying between the different influenza types/subtypes and seasons. Studies show vaccine efficacy/effectiveness values of 50%-70% in pregnant women and 20%-90% in young children against lab-confirmed influenza, although the efficacy/effectiveness depended on the study design, host factors, vaccine type, manufacturing practices, and the antigenic match/mismatch between the influenza vaccine strains and the circulating strains. Current evidence suggests that the benefits of IIVs far outweigh the potential risks and that IIVs should be recommended for pregnant women and young children.

Direct and indirect effects of COVID-19 on perinatal outcomes in low- and middle-income countries

Similar to previous outbreaks, the coronavirus disease 2019 (COVID-19) pandemic will have both direct and indirect effects on perinatal outcomes, especially in low- and middle-income countries. Limited data on the direct impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy shows women who are Black, obese and with co-morbidities are at higher risk of hospitalisation due to COVID-19. Younger age groups in Africa and South Asia have shown increased COVID-19 mortality. Indigenous pregnant women in Pacific Island countries are likely to be high risk for severe outcomes from COVID-19 due to high rates of diabetes and obesity. It is important to involve pregnant women in research, especially with regards to vaccine development and therapeutics.

Comparison of influenza antibody titers among women who were vaccinated in the 2nd and the 3rd trimesters of pregnancy

BACKGROUND

We compared cord blood antibody titers in unvaccinated pregnant women to those vaccinated with seasonal influenza vaccine during the 2^nd and the 3^rd trimesters.

METHODS

Pregnant women had cord blood collected at delivery for hemagglutination inhibition assay against vaccine reference viruses: A/California/07/2009 (H1N1)pdm09, A/Switzerland/9715293/2013 (H3N2), and B/Phuket/3073/2013 (Yamagata lineage). Geometric mean titer (GMT) ratios were calculated comparing vaccinated versus unvaccinated pregnant women, and women vaccinated in the 2^nd and the 3^rd trimesters. Proportions of women achieving defined titers were compared using the χ² test.

RESULTS

Of 307 women, 190 (62%) were unvaccinated. Fifty and 67 were vaccinated during the 2^nd and the 3^rd trimesters, respectively. Median enrollment age was 29 years (interquartile range 24-34). Sixteen (5%) women had pre-existing conditions, but none were immunocompromised. GMT ratios comparing vaccinated and unvaccinated women were 5.90 (95% confidence interval [CI] 5.06-6.96) for influenza A/California, 5.39 (95% CI 4.18-6.08) for influenza A/Switzerland, and 5.05 (95% CI 4.43-5.85) for influenza B/Phuket. Similarly, the GMT ratios comparing the 3^rd and the 2^nd trimester vaccinated women were 2.90 (95% CI 2.54-3.39), 2.82 (95% CI 2.56-3.13), and 2.83 (95% CI 2.56-3.14), respectively. The proportions of women with defined titers for the three vaccine reference viruses did not differ between 2^nd and 3^rd trimester vaccinated women (titers ≥40: 68-92% versus 70-93%; ≥110: 32% versus 33-63%; and ≥330: 4-10% versus 3-21%).

CONCLUSIONS

Pregnant women vaccinated against influenza had more placental transfer of influenza antibodies to their infants than unvaccinated women. Placental transfer of antibodies was higher among those vaccinated in the 3^rd trimester than in the 2^nd trimester. There was no difference in the proportions of women achieving antibody titers corresponding to protection against influenza in children. Findings support the current World Health Organization's recommendation that pregnant women may be vaccinated in either 2^nd or 3^rd trimester of pregnancy.

Safety and protective effects of maternal influenza vaccination on pregnancy and birth outcomes: A prospective cohort study

BACKGROUND

Our study aimed to assess the safety and protective effect of maternal influenza vaccination on pregnancy and birth outcomes.

METHODS

The study population comprised 1253 healthy nulliparous pregnant women in South Australia between 2015 and 2018. Participants were followed prospectively, with vaccination status (confirmed by medical records), pregnancy, and birth outcome data collected by midwives. Adjusted relative risks (aRRs) and adjusted hazard ratios (aHRs) were estimated accounting for time-varying vaccine exposure and temporal nature of each outcome.

FINDINGS

Maternal influenza vaccination (48%, 603 of 1253) reduced the risk for pre-delivery hospitalisation with influenza like illness (aHR 0•61; 95% CI 0•39, 0•97). Maternal influenza vaccination was not associated with spontaneous abortion (aHR 0•42, 95% CI 0•12, 1•45), chorioamnionitis (aRR 0•78, 95% CI, 0•32, 1•88), gestational hypertension (aHR 0•78, 95% CI 0•47, 1•29), pre-eclampsia (aHR 0.84, 95% CI 0•54, 1•27), gestational diabetes (aHR 1•16, 95% CI 0•82, 1•66) nor preterm birth (aHR 0•94, 95% CI 0•59, 1•49). No associations between antenatal influenza vaccination and congenital anomalies, admission to the neonatal care unit, low Apgar scores, and mechanical ventilation were observed. Results were not materially changed after adjustment for pertussis vaccination. We observed a protective effect of maternal influenza vaccination on low birth weight (aHR 0•46, 95% CI 0•23, 0•94) and a marginal protective effect on small for gestational age births (aHR 0•65, 95% CI 0•40, 1•04) during periods of high influenza activity.

INTERPRETATION

These results support the safety of maternal influenza vaccination and suggest a protective effect in reducing the rates of low birthweight and small for gestational age births.

FUNDING

There was no funding for this study.

Direct and indirect effects of COVID-19 on perinatal outcomes in low- and middle-income countries

Similar to previous outbreaks, the coronavirus disease 2019 (COVID-19) pandemic will have both direct and indirect effects on perinatal outcomes, especially in low- and middle-income countries. Limited data on the direct impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy shows women who are Black, obese and with co-morbidities are at higher risk of hospitalisation due to COVID-19. Younger age groups in Africa and South Asia have shown increased COVID-19 mortality. Indigenous pregnant women in Pacific Island countries are likely to be high risk for severe outcomes from COVID-19 due to high rates of diabetes and obesity. It is important to involve pregnant women in research, especially with regards to vaccine development and therapeutics.

COVID-19 and Advanced Practice Registered Nurses: Frontline Update

Coronavirus disease 2019 (COVID-19) emerged in 2019 and rapidly became a global pandemic, infecting millions and killing hundreds of thousands. The disease altered the practices of hospitals, clinics, and patients. These changes have implications for advanced practice registered nurses (APRNs). APRNs must remain current on best practices for treatment and diagnosis of COVID-19 while being cognizant of changes to their scope of practice. As the pandemic continues, APRNs will remain on the front lines treating patients with COVID-19 while also caring for vulnerable populations within the community. To provide high-quality care, APRNs must use a multifaceted approach that heeds ongoing updates to evidence-based practice.

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Advanced practice registered nurses (APRNs) are on the front line of treatment of coronavirus disease 2019 (COVID-19).

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APRNs can help with physical and psychologic issues caused by COVID-19.

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APRNs must regularly review updates on COVID-19 due to rapidly changing guidelines.

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Vulnerable populations will face unique challenges from the pandemic.

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COVID-19 affects the mental health of the general population and providers.

Effectiveness of quadrivalent influenza vaccine in pregnant women and infants, 2018-2019

Influenza is associated with an increased risk for serious illness, hospitalization and/or death in pregnant women and young infants. We prospectively studied the effectiveness of a quadrivalent inactivated influenza vaccine (QIV) in pregnant women and their infants during the 2018-2019 influenza season. A QIV was offered to pregnant women cared in a maternity hospital in Athens. Women were contacted weekly by telephone during the influenza season and PCR test was offered to women or infants who developed influenza-like illness (ILI). We studied 423 pregnant women and 446 infants. Unvaccinated pregnant women had a 7.5% probability to develop laboratory-confirmed influenza compared to 2.1% among vaccinated women (Odds ratio: 3.6; confidence intervals: 1.14-11.34, p-value = 0.029). Infants whose mothers were not vaccinated had a 7.9% probability to develop laboratory-confirmed influenza compared to 2.8% among infants of vaccinated mothers (Odds ratio = 2.849, confidence intervals: 0.892-9.102, p-value = 0.053). Cox regression analyses showed that QIV vaccination was significantly associated with a decreased probability for laboratory-confirmed influenza, ILI, healthcare seeking and hospitalization among pregnant women and a decreased probability for laboratory-confirmed influenza, healthcare seeking and prescription of antibiotics among infants. The effectiveness of QIV against laboratory-confirmed influenza was 72% among pregnant women and 64.5% among infants during the 2018-2019 influenza season. Vaccination of pregnant women with the QIV was associated with a lower risk for laboratory-confirmed influenza for them and their infants during the influenza season. Our findings strongly support the World Health Organization recommendations for vaccinating pregnant women against influenza.

Baseline incidence of adverse birth outcomes and infant influenza and pertussis hospitalisations prior to the introduction of influenza and pertussis vaccination in pregnancy: a data linkage study of 78 382 mother-infant pairs, Northern Territory, Australia, 1994-2015

We conducted probabilistic data linkage of three population datasets for the Northern Territory (NT), Australia, to describe the incidence of preterm births, stillbirths, low birthweight and small for gestational age (SGA) per 1000 NT births; and influenza and pertussis hospitalisations per 1 00 000 NT births in infants <7 months of age, in a pre-maternal vaccination era. The Perinatal Trends dataset (1994–2014) formed the cohort of 78 382 births. Aboriginal mother–infant pairs (37%) had disproportionately higher average annual rates (AR) for all adverse birth outcomes compared to their non-Aboriginal counterparts; rate ratios: preterm births 2.2 (AR 142.4 vs. 64.7); stillbirths 2.3 (AR 10.8 vs. 4.6); low birthweight 2.9 (AR 54 vs. 19); and SGA 1.7 (AR 187 vs. 111). Hospitalisation (2000–2015) and Immunisation Register datasets (1994–2015), showed that influenza hospitalisations (n = 53) and rates were 42.3 times higher in Aboriginal infants (AR 254 vs. 6); and that pertussis hospitalisations (n = 37) were 7.1 times higher in Aboriginal infants (AR 142.5 vs. 20.2) compared to non-Aboriginal infants. These baseline data are essential to assess the safety and effectiveness of influenza and pertussis vaccinations in pregnant women from the NT. Remote living Aboriginal women and infants stand to benefit the most from these vaccines.

ACOG Committee Opinion No. 753: Assessment and Treatment of Pregnant Women With Suspected or Confirmed Influenza

Pregnant and postpartum women are at high risk of serious complications of seasonal and pandemic influenza infection. Pregnancy itself is a high-risk condition, making the potential adverse effects of influenza particularly serious in pregnant women. If a pregnant woman has other underlying health conditions, the risk of adverse effects from influenza is even greater. Antiviral treatment is necessary for all pregnant women with suspected or confirmed influenza, regardless of vaccination status. Obstetrician-gynecologists and other obstetric care providers should promptly recognize the symptoms of influenza, adequately assess severity, and readily prescribe safe and effective antiviral therapy for pregnant women with suspected or confirmed influenza. Over-the-phone treatment for low-risk patients is preferred to help reduce the spread of disease among other pregnant patients in the office. Obstetrician-gynecologists and other obstetric care providers should treat pregnant women with suspected or confirmed influenza with antiviral medications presumptively based on clinical evaluation, regardless of vaccination status or laboratory test results. Pregnant women with suspected or confirmed influenza infection should receive antiviral treatment with oseltamivir or zanamivir based on the current resistance patterns. Treatment within 48 hours of the onset of symptoms is ideal but treatment should not be withheld if the ideal window is missed. Because of the high potential for morbidity and mortality for pregnant and postpartum patients, the Centers for Disease Control and Prevention advises that postexposure antiviral chemoprophylaxis can be considered for pregnant women and women who are up to 2 weeks postpartum (including after pregnancy loss) who have had close contact with infectious individuals.

Determinants of influenza and pertussis vaccine uptake in pregnant women in Ireland: A cross-sectional survey in 2017/18 influenza season

In Ireland seasonal influenza and pertussis vaccination during pregnancy is recommended and every year national campaigns are organised to raise awareness and improve uptake. We estimated influenza and pertussis vaccine uptake and identified factors associated with vaccination status in pregnant women in 2017/18. We conducted a face-to-face omnibus survey, with quota sampling, among women aged 18-55 years and collected socio-demographic characteristics, self-reported vaccination status, awareness of vaccine campaigns, and attitudes towards vaccination. Sample was weighted to ensure representativeness with the target population. We performed univariate and multivariable logistic regression analyses on survey data. Overall, 241 pregnant women were enrolled. Influenza and pertussis vaccine uptake was 61.7% and 49.9%, respectively. Awareness of vaccine campaign and socio-economic status (SES) were associated with both influenza and pertussis vaccine uptake. The association between SES and uptake of vaccines differed by awareness. Women aware of the influenza vaccine campaign and with mid and low SES were less likely to be vaccinated, compared to those with high SES (aOR = 0.46; 95%CI: 0.22-0.97; aOR = 0.27; 95%CI: 0.12-0.60, respectively); women not aware of the pertussis vaccine campaign and with mid and low SES were less likely to be vaccinated, compared to those aware and with high SES (aOR = 0.15; 95%CI: 0.04-0.48; aOR = 0.05; 95%CI: 0.01-0.24, respectively). General practitioner (GP) recommendation was the main reason for receiving influenza vaccine (39.2%), and 71.8% of women were recommended pertussis vaccination from their GPs. The survey reports moderate uptake of vaccines among pregnant women, inequalities in uptake by SES and identifies GPs as primary source for vaccine recommendation. We recommend multifaceted campaigns, by engaging GPs, to target all socio-economic groups.

ACOG Committee Opinion No. 732: Influenza Vaccination During Pregnancy

Influenza vaccination is an essential element of prepregnancy, prenatal, and postpartum care because influenza can result in serious illness, including a higher chance of progressing to pneumonia, when it occurs during the antepartum or postpartum period. In addition to hospitalization, pregnant women with influenza are at increased risk of intensive care unit admission and adverse perinatal and neonatal outcomes. The Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices and the American College of Obstetricians and Gynecologists recommend that all adults receive an annual influenza vaccine and that women who are or will be pregnant during influenza season receive an inactivated influenza vaccine as soon as it is available. In the United States, the influenza season typically occurs from October to May. Ideally, an influenza vaccination should be given before the end of October, but vaccination throughout the influenza season is encouraged to ensure protection during the period of circulation. Any of the licensed, recommended, age-appropriate, inactivated influenza vaccines can be given safely during any trimester. Therefore, it is critically important that obstetrician-gynecologists and other obstetric care providers recommend and advocate for the influenza vaccine. Obstetrician-gynecologists are encouraged to stock and administer the influenza vaccine to their pregnant patients in their offices, and should get the influenza vaccine themselves every season. If the influenza vaccine cannot be offered in a practice, obstetrician-gynecologists and obstetric care providers should refer patients to another health care provider, pharmacy, or community vaccination center. This updated Committee Opinion includes more recent data on the safety and efficacy of influenza vaccination during pregnancy and recommendations for treatment and postexposure chemoprophylaxis.

'Links2HealthierBubs' cohort study: protocol for a record linkage study on the safety, uptake and effectiveness of influenza and pertussis vaccines among pregnant Australian women

INTRODUCTION

Pregnant women and infants are at risk of severe influenza and pertussis infection. Inactivated influenza vaccine (IIV) and diphtheria-tetanus-acellular pertussis vaccine (dTpa) are recommended during pregnancy to protect both mothers and infants. In Australia, uptake is not routinely monitored but coverage appears sub-optimal. Evidence on the safety of combined antenatal IIV and dTpa is fragmented or deficient, and there remain knowledge gaps of population-level vaccine effectiveness. We aim to establish a large, population-based, multi-jurisdictional cohort of mother-infant pairs to measure the uptake, safety and effectiveness of antenatal IIV and dTpa vaccines in three Australian jurisdictions. This is a first step toward assessing the impact of antenatal vaccination programmes in Australia, which can then inform government policy with respect to future strategies in national vaccination programmes. METHODS AND ANALYSIS: 'Links2HealthierBubs' is an observational, population-based, retrospective cohort study established through probabilistic record linkage of administrative health data. The cohort includes births between 2012 and 2017 (~607 605 mother-infant pairs) in jurisdictions with population-level antenatal vaccination and health outcome data (Western Australia, Queensland and the Northern Territory). Perinatal data will be the reference frame to identify the cohort. Jurisdictional vaccination registers will identify antenatal vaccination status and the gestational timing of vaccination. Information on maternal, fetal and child health outcomes will be obtained from hospitalisation and emergency department records, notifiable diseases databases, developmental anomalies databases, birth and mortality registers.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the Western Australian Department of Health, Curtin University, the Menzies School of Health Research, the Royal Brisbane and Women's Hospital, and the West Australian Aboriginal Health Ethics Committees. Research findings will be disseminated in peer-reviewed journals, at scientific meetings, and may be incorporated into communication materials for public health agencies and the public.

Influenza Vaccination Coverage Among Pregnant Women in the U.S., 2012-2015

INTRODUCTION

Pregnant women are at increased risk for severe illness from influenza and influenza-related complications. Vaccinating pregnant women is the primary strategy to protect them and their infants from influenza. This study aims to assess influenza vaccination coverage during three influenza seasons (2012-2015) from a national probability-based sampling survey and evaluate potential factors that influence vaccination uptake among pregnant women.

METHODS

Data from the 2012 through 2015 National Health Interview Surveys were analyzed in 2017. Pregnant women aged 18-49 years were included in the analysis. The Kaplan-Meier survival analysis procedure was used for vaccination coverage in each season. Bivariate and multivariable logistic regression analyses were performed to examine factors associated with vaccination. Adjusted vaccination coverage and adjusted prevalence ratios are reported with corresponding 95% CIs.

RESULTS

In the 2012-2013, 2013-2014, and 2014-2015 influenza seasons, 40.4%, 45.4%, and 43.1% of pregnant women were vaccinated, respectively. Multivariable analysis indicated that factors independently associated with a lower likelihood of vaccination included having only a high school education, having three or less provider visits, and having no usual place of care (p<0.05). Less than half of women with ten or more visits were vaccinated (48.6%).

CONCLUSIONS

Vaccination coverage among pregnant women from this nationally representative sample was suboptimal during recent influenza seasons. Vaccination coverage was lower among certain sociodemographic, access-to-care subgroups. Multifactorial vaccination barriers may exist. Interventions, such as assessing vaccination history at every visit and implementing reminder-recall systems, standing orders, and addressing vaccination hesitancy, are needed to increase vaccination uptake among pregnant women.

Burden, effectiveness and safety of influenza vaccines in elderly, paediatric and pregnant populations

Vaccination is the most practical means available for preventing influenza. Influenza vaccines require frequent updates to keep pace with antigenic drift of the virus, and the effectiveness, and sometimes the safety, of the vaccine can therefore vary from season to season. Three key populations that the World Health Organization recommends should be prioritized for influenza vaccination are pregnant women, children younger than 5 years of age and the elderly. This review discusses the burden of influenza and the safety and effectiveness profile of influenza vaccines recommended for these groups.

Effectiveness of inactivated quadrivalent influenza vaccine in the 2015/2016 season as assessed in both a test-negative case-control study design and a traditional case-control study design

Both traditional case-control studies (TCCSs) and test-negative case-control studies (TNCCSs) are commonly used to assess influenza vaccine effectiveness (VE). To compensate for the fact that observational studies are susceptible to bias, we combined both methods to assess VE in one geographical area during the 2015/2016 season, when influenza A (H1N1)pdm was dominant. Our TNCCS covered 331 children aged 6 months to 15 years who visited our hospital with fever, including 182 with influenza, and our TCCS covered 812 pediatric outpatients aged 6 months to 15 years, including 214 with influenza. Influenza infection and vaccination history were reviewed, and VE was calculated as (1 - odds ratio) × 100. In the TNCCS, VE against influenza A was 68% (95% CI 47-81) overall, and 70% (48-83) for those given two doses; against influenza B, VE was 37% (- 12-64) overall and 49% (2-74) for two doses. In the TCCS, VE against influenza A was 44% (15-63) overall and 44% (13-64) for two doses, and VE against influenza B was 24% (- 19-52) overall and 41% (3-64) for two doses.

CONCLUSION

Both studies confirmed significant VE against influenza A, significant two-dose VE against influenza B, and better two-dose VE than one-dose VE. What is Known: • Influenza vaccine effectiveness (VE) varies from year to year. • Observational studies are conventionally used for VE assessment. However, they are inherently susceptible to bias and confounding. What is New: • This is the first report of influenza VE assessment using more than one observational study and performed in a specific area during the same season. • VE estimates obtained in our traditional case-control study were lower than those in our test-negative case-control study, but both studies found significant VE against influenza.

Influenza vaccine effectiveness among high-risk groups: A systematic literature review and meta-analysis of case-control and cohort studies

Vaccination represents the most effective intervention to prevent infection, hospitalization and mortality due to influenza. This meta-analysis quantifies data reporting influenza vaccine effectiveness (VE) on influenza visits and hospitalizations of case-control and cohort studies among high-risk groups.

A systematic literature review including original articles published between 2007 and 2016, using a protocol registered on Prospero with No. 42017054854, and a meta-analysis were conducted.

For 3 high-risk groups (subjects with underlying health conditions, pregnant women and health care workers) only a qualitative evaluation was performed. The VE quantitative analysis demonstrated a clear significant overall effect of 39% (95%CI: 32–46%) for visits and 57% (95%CI: 30–74%) for hospitalization among children. Considering the elderly influenza VE had a clear effect of 25% (95%CI: 6–40%) for visits and 14% (95%CI: 7–21%; p<0.001) for hospitalization.

This study showed the high VE of influenza vaccination among high-risk groups, representing a tool for public health decision-makers to develop evidence-based preventive interventions to avoid influenza outcomes.

A Phase 2 randomized, observer-blind, placebo-controlled, dose-ranging trial of aluminum-adjuvanted respiratory syncytial virus F particle vaccine formulations in healthy women of childbearing age

OBJECTIVE

Respiratory syncytial virus (RSV) causes significant morbidity and mortality in infants. We are developing an RSV fusion (F) protein nanoparticle vaccine for immunization of third trimester pregnant women to passively protect infants through transfer of RSV-specific maternal antibodies. The present trial was performed to assess the immunogenicity and safety of several formulations of RSV F vaccine in 1-dose or 2-dose schedules.

METHODS

Placebo, or vaccine with 60μg or 120μg RSV F protein and 0.2, 0.4, or 0.8mg aluminum, were administered intramuscularly on Days 0 and 28 to healthy women 18-35years old. Immunogenicity was assessed from Days 0 through 91 based on anti-F IgG and palivizumab-competitive antibody (PCA) by ELISA, and RSV A and B neutralizing antibodies by microneutralization (MN) assay. Solicited adverse events were collected through Day 7 and unsolicited adverse events through Day 91.

RESULTS

All formulations were well-tolerated, with no treatment-related serious adverse events. Anti-F IgG and PCA responses were correlated and increased after both doses, while MN increased significantly only after the first dose, then plateaued. The timeliest and most robust antibody responses followed one dose of 120μg RSV F protein and 0.4mg aluminum, but persistence through 91days was modestly (∼25%) superior following two doses of 60μg RSV F protein and 0.8mg aluminum. Western blot analysis showed RSV infections in active vaccinees were reduced by 52% overall (p=0.009 overall) over the Day 0 through 90 period.

CONCLUSIONS

RSV F nanoparticle vaccine formulations were well tolerated and immunogenic. The optimal combination of convenience and rapid response for immunization in the third trimester occurred with 120μg RSV F and 0.4mg aluminum, which achieved peak immune responses in 14days and sufficient persistence through 91days to allow for passive transfer of IgG antibodies to the fetus. NCT01960686.

Protection of children against influenza: Emerging problems

Influenza is a common disease and in children it can be severe enough to lead to hospitalization and death. Protection of all children against influenza, particularly the youngest, is strongly recommended by most health authorities. However, available vaccines cannot be used in the first 6 months of age, a period of life characterized by the highest risk of influenza-related complications. Maternal immunization is an attractive possibility to overcome this problem. For years, protection against influenza has been pursued by administering the trivalent inactivated vaccine given intramuscularly (IIV3). More recently, a trivalent live attenuated influenza vaccine (LAIV3) administered intranasally was licensed and adopted in a number of countries as an alternative to IIV3. In recent years, to increase protection and include a second B strain, quadrivalent inactivated (IIV4) and live attenuated vaccines (LAIV4) were prepared and licensed. However, during the 2015-2016 season the effectiveness of LAIVs was debated, and they were withdrawn from the list of recommended influenza vaccines in the USA. This review presents an update on the evidence related to the protection of infants against influenza through maternal immunization and the effectiveness of LAIV. Available data indicates that despite maternal immunization, a number of children have no protective antibody levels at birth, and in the majority of children with antibody protection, it is limited to the first 8 weeks of the postnatal period. Moreover, data on LAIV effectiveness in the pediatric population must be clarified because this vaccine can significantly improve vaccination coverage in children.