Neonatal outcomes after influenza immunization during pregnancy: a randomized controlled trial

Prenatal Maternal Immunization for Infant Protection: A Review of the Vaccines Recommended, Infant Immunity and Future Research Directions

Prenatal maternal immunization is an effective tool to protect mothers and infants from poor health outcomes due to infectious diseases. We provide an overview of the rationale for the use of prenatal vaccines, discuss the immunologic environment of the maternal-fetal interface including the impact of maternal vaccines prenatally and subsequently on the infant's immune response, and review vaccines currently recommended in pregnancy and landscape for the future of maternal vaccination. This review aims to provide an understanding of the recent history and progress made in the field and highlight the importance of continued research and development into new vaccines for pregnant populations.

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.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

INTERPRETATION

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

Responding to Higher-Than-Expected Infant Mortality Rates from Respiratory Syncytial Virus (RSV): Improving Treatment and Reporting Strategies

Respiratory syncytial virus (RSV) has a major role in respiratory infections in young infants around the world. However, substantial progress has been made in recent years in the field of RSV. A wide variety of observational studies and clinical trials published in the past decade provide a thorough idea of the health and economic burden of RSV disease in the developing world. In this review, we discuss the impact of RSV burden of disease, major gaps in disease estimations, and challenges in generating new therapeutic options and an immune response against the virus, and briefly describe next generation technologies that are being evaluated.

Biological Sex and Pregnancy Affect Influenza Pathogenesis and Vaccination

Males and females differ in the outcome of influenza A virus (IAV) infections, which depends significantly on age. During seasonal influenza epidemics, young children (< 5 years of age) and aged adults (65+ years of age) are at greatest risk for severe disease, and among these age groups, males tend to suffer a worse outcome from IAV infection than females. Following infection with pandemic strains of IAVs, females of reproductive ages (i.e., 15-49 years of age) experience a worse outcome than their male counterparts. Although females of reproductive ages experience worse outcomes from IAV infection, females typically have greater immune responses to influenza vaccination as compared with males. Among females of reproductive ages, pregnancy is one factor linked to an increased risk of severe outcome of influenza. Small animal models of influenza virus infection and vaccination illustrate that immune responses and repair of damaged tissue following IAV infection also differ between the sexes and impact the outcome of infection. There is growing evidence that sex steroid hormones, including estrogens, progesterone, and testosterone, directly impact immune responses during IAV infection and vaccination. Greater consideration of the combined effects of sex and age as biological variables in epidemiological, clinical, and animal studies of influenza pathogenesis is needed.

Trends of influenza vaccination coverage in pregnant women: a ten-year analysis from a French healthcare database

Pregnant women have a high risk of severe influenza, associated with obstetrical complications. The World Health Organization (WHO) has recommended influenza vaccination for all pregnant women since 2012. The vaccination coverage remains low worldwide, and in Europe, due to a lack of proposition from the health care providers, and a high refusal rate from the women. The primary aim of this study was to estimate the influenza vaccination coverage (IVC) in a population of pregnant women in France, and to analyse its evolution from 2009 to 2018. The secondary objective was to describe the vaccinated population and to find determinants associated with the vaccination. This retrospective cohort study is based on the EGB French health care database, a representative sample of the French population containing data from the health insurance system. All pregnant women who delivered medically or spontaneously over the 2009–2018 period were included. In the 2009–2018 period, only 1.2% pregnant women were vaccinated against influenza (n = 875/72,207; 95% CI 1.14–1.30). The IVC slightly increased after the 2012 WHO recommendation, from 0.33 to 1.79% (p < 0.001) but remained extremely low (4.1% in 2018). Women younger than 25 years old had a low coverage (0.6%) whereas women over 35 years old were more likely to get the influenza vaccine (1.7%; OR: 2.82, 95% CI 2.14–3.71). The vaccination behavior was not influenced by multifetal pregnancy or parity, but socio-economically deprived women were less likely to be vaccinated (OR: 0.81, 95% CI: 0.67–0.98). Women with pre-existing medical conditions had an overall higher vaccination rate (2.5%; OR: 2.32, 95% CI: 1.94–2.77). The vaccine was mainly prescribed by family physicians (58%). Influenza vaccination in pregnant women in France remains very low, particularly in younger, healthy women, and measures such as information campaigns towards pregnant women and studies of the knowledge, attitudes, and practices of the health care professionals need to be undertaken to improve the coverage.

Educational and economic returns to cognitive ability in low- and middle-income countries: A systematic review

There is growing interest to use early cognitive ability to predict schooling and employment outcomes in low- and middle-income countries (LMICs). Rather than using educational attainment and school enrollment as predictors of future economic growth or of improving an individual's earning potential, mounting evidence suggests that cognitive ability may be a better predictor. The relationship between cognitive ability, education, and employment are essential to predict future development in LMICs. We performed a systematic literature review and meta-analysis of the evidence regarding the relationship between cognitive ability and educational outcomes, and between cognitive ability and economic outcomes across LMICs. We searched peer-reviewed studies since 2000 that quantitatively measured these relationships. Based on an initial search of 3,766 records, we identified 14 studies, including 8 studies that examined the cognition-education link and 8 studies that assessed cognition-employment returns in LMICs. Identified studies showed that higher cognitive ability increased the probability of school enrollment, academic achievement, and educational attainment across LMICs. A meta-analysis of returns to wages from cognitive ability suggested that a standard deviation increase in cognitive test scores was associated with a 4.5% (95% CI 2.6%-9.6%) increase in wages. Investments into early cognitive development could play a critical role in improving educational and economic outcomes in LMICs. Further research should focus particularly in low-income countries with the least evidence, and examine the impact on education and economic outcomes by cognitive domains to provide more robust evidence for policy makers to take action.

Does Influenza Vaccination during Pregnancy Have Effects on Non-Influenza Infectious Morbidity? A Systematic Review and Meta-Analysis of Randomised Controlled Trials

The recommendation to provide inactivated influenza vaccine (IIV) to pregnant women is based on observed protection against influenza-related morbidity in mother and infant. Non-live vaccines may have non-specific effects (NSEs), increasing the risk of non-targeted infections in females. We reviewed the evidence from available randomised controlled trials (RCTs) of IIV to pregnant women, to assess whether IIV may have NSEs. Four RCTs, all conducted in low- and middle-income settings, were identified. We extracted information on all-cause and infectious mortality and adverse events in women and their infants. We conducted meta-analyses providing risk ratios (RR). The meta-analysis for maternal all-cause mortality provided a RR of 1.48 (95% CI = 0.52–4.16). The estimates for miscarriage/stillbirth and infant all-cause mortality up to 6 months of age were 1.06 (0.78–1.44) and 1.11 (0.87–1.41), respectively. IIV was associated with a higher risk of non-influenza infectious adverse events, with meta-estimates of 2.01 (1.15–3.50) in women and 1.36 (1.12–1.67) in infants up to 6 months of age. Thus, following a pattern seen for other non-live vaccines, IIV was associated with a higher risk of non-influenza infectious adverse events. To ensure that scarce resources are used well, and no harm is inflicted, further RCTs are warranted.

Vaccine package inserts and prescribing habits of obstetricians-gynecologists for maternal vaccination

Despite ample evidence of the safety and efficacy of the influenza vaccine and the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine during pregnancy, two-thirds of pregnant women do not receive these vaccines. Providers have a significant role in increasing prenatal vaccine uptake. It is important to understand how different sources of vaccine prescribing information, such as Food and Drug Administration package inserts, influence provider recommendations. We aimed to examine the role of vaccine package inserts in provider recommendations and perceptions of safety and effectiveness of vaccines during pregnancy. A cross-sectional survey was mailed to a random, weighted sample of American College of Obstetricians and Gynecologists Fellows living in the United States in March 2019. Providers were asked about their attitudes toward package inserts, and to evaluate sample package insert statements following two different labeling rules. Their evaluations of each rule were then compared. Of the 321 respondents, the majority (90%, 288/321) recommended and/or administered maternal vaccinations. Few respondents (7.8%, 25/321) read package inserts for information regarding vaccination. Respondents were less likely to recommend sample vaccines with Pregnancy and Lactation Labeling Rule-complying inserts (46.1%, 148/321) than vaccines with Pregnancy Category inserts (87.5%, 282/321). Although most providers did not actively utilize vaccine package inserts to inform recommendations, the previous Pregnancy Categories rule was preferred compared to the Pregnancy and Lactation Labeling Rule. Collaborative efforts to update inserts with current clinical practices for pregnancy would be valuable in reducing apprehensiveness around package inserts to generate safer and more cogent recommendations for pregnant women.

Methodologic approaches in studies using real-world data (RWD) to measure pediatric safety and effectiveness of vaccines administered to pregnant women: A scoping review

OBJECTIVE

This scoping review mapped studies using real-world data (RWD) to measure pediatric safety and effectiveness of vaccines administered to pregnant women.

INTRODUCTION

In the US, two vaccines are recommended for all pregnant women to prevent illness in the infant: inactivated influenza vaccine (recommended since 2004), and the combined tetanus-diphtheria-acellular pertussis (Tdap) vaccine (recommended since 2013). This scoping review maps the studies conducted to date that address questions about pediatric safety and effectiveness of vaccines administered during pregnancy and provides a knowledge base for evaluating the use of RWD to study this issue.

METHODS

The scoping review was conducted following a published protocol. Methods included an electronic search of PubMed and Embase, screening of titles and abstracts by two reviewers, and double extraction of data for summary and synthesis. Studies that reported on pregnant women and the effectiveness or safety outcomes in their infants were included.

RESULTS

Forty-eight studies met the inclusion criteria of the scoping review protocol using RWD to assess safety or effectiveness of influenza or pertussis vaccinations administered to pregnant women with respect to pregnancy, infant or child outcomes. Detailed information about data sources, linkage of maternal and infant data, and operational definitions for gestational age were largely absent from the majority of studies raising concerns about reproducibility and validity of study findings.

CONCLUSIONS

A body of literature is available from which to plan and design future studies of vaccination in pregnant women using RWD. This is of intense importance as new vaccines, such as those for COVID-19, become available to the general population via approval or authorization without inclusion of pregnant women in the clinical trials.

Efficacy and safety of influenza vaccination during pregnancy: realizing the potential of maternal influenza immunization

Introduction: Pregnant women are at higher risk of severe complications following influenza infection compared to the general population. Influenza vaccination during pregnancy can offer direct protection to pregnant women and passive immunity to infants up to 6 months of age via maternal antibodies. Pregnant women are a high priority group for influenza immunization.Areas covered: This review provides an overview of the basis for recommending influenza vaccine to pregnant women, current immunization policies, the evidence supporting the safety and effectiveness of maternal vaccination, and future research needed. We conducted a search of PubMed for articles describing the safety or efficacy of influenza vaccines administered during pregnancy. Published articles from inception to 17 November 2020 were reviewed.Expert opinion: Experimental and observational evidence support the efficacy, effectiveness and safety of influenza immunization during pregnancy. These data support the continued provision of inactivated influenza vaccine to pregnant women, as recommended by global immunization policies. To achieve success with maternal influenza immunization programs, further work is needed to inform policy development in low- and middle-income settings and implementation and promotion in high-income settings.

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.

Vaccination of pregnant women against influenza: what is the optimal timing?

Pregnant women and young infants are at increased risk for severe influenza and its complications. Influenza vaccination during pregnancy is increasingly implemented as a strategy aiming to protect the pregnant woman, the fetus and the young infant. In clinical practice, the achievement of satisfactory protection for the pregnant woman without compromising the protection of her infant during the first months of life remains a challenge. Determinants that are implicated in the optimal timing of influenza vaccination in pregnancy include influenza season, trimester of pregnancy, maternal host factors and infant factors. This article addresses influenza vaccination in pregnancy and presents recent published evidence on issues that affect the optimization of the timing of maternal vaccination.

A Retrospective observational cohort study of the effect of antenatal influenza vaccination on birth outcomes in Cape Town, South Africa, 2015-2016

Background

There are conflicting data concerning the impact of antenatal influenza vaccination on birth outcomes including low birthweight (LBW), preterm birth, small for gestational age (SGA), and stillbirth.

Methods

We conducted a retrospective observational cohort study of infants born to women residing in Mitchells Plain, Cape Town. Infants were born at 4 health facilities during May 28 – December 31, 2015 and April 15 – December 31, 2016. We performed crude and multivariable logistic regression, propensity score (PS) matching logistic regression, and inverse probability of treatment weighted (IPTW) regression to assess vaccine effectiveness (VE) against LBW, preterm birth, SGA, and stillbirth adjusting for measured confounders.

Results

Maternal vaccination status, antenatal history, and ≥1 birth outcome(s) were available for 4084/5333 (76.6%) pregnancies, 2109 (51.6%) vaccinated, and 1975 (48.4%) unvaccinated. The proportion LBW was lower in vaccinated (6.9%) vs. unvaccinated (12.5%) in multivariable [VE 0.27 (95% CI 0.07‐0.42)], PS [VE 0.30 (95% CI 0.09‐0.51)], and IPTW [VE 0.24 (95% CI 0.04‐0.45)]. Preterm birth was less frequent in vaccinated (8.6%) than unvaccinated (16.4%) in multivariable [VE 0.26 (0.09‐0.40)], PS [VE 0.25 (95% CI 0.09‐0.41)], and IPTW [VE 0.34 (95% CI 0.18‐0.51)]. The proportion SGA was lower in vaccinated (6.0%) than unvaccinated (8.8%) but not in adjusted models. There were few stillbirths in our study population, 30/4084 (0.7%).

Conclusions

Using multiple analytic approaches, we found that influenza vaccination was associated with lower prevalence of LBW (24‐30%) and preterm birth (25‐34%) in Cape Town during 2015‐2016.

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.

Efficacy, duration of protection, birth outcomes, and infant growth associated with influenza vaccination in pregnancy: a pooled analysis of three randomised controlled trials

Background

Maternal influenza immunisation can reduce morbidity and mortality associated with influenza infection in pregnant women and young infants. We aimed to determine the vaccine efficacy of maternal influenza immunisation against maternal and infant PCR-confirmed influenza, duration of protection, and the effect of gestational age at vaccination on vaccine efficacy, birth outcomes, and infant growth up to 6 months of age.

Methods

We did a pooled analysis of three randomised controlled trials done in Nepal (2011–2014), Mali (2011–2014), and South Africa (2011–2013). Pregnant women, gestational age 17–34 weeks in Nepal, 28 weeks or more in Mali, and 20–36 weeks in South Africa, were enrolled. Women were randomly assigned 1:1 to a study group, in which they received trivalent inactivated influenza vaccine (IIV) in all three trials, or a control group, in which they received saline placebo in Nepal and South Africa or quadrivalent meningococcal conjugate vaccine in Mali. Enrolment at all sites was complete by April 24, 2013. Infants and women were assessed for respiratory illness, and samples from those that met the case definition were tested for influenza by PCR testing. Growth measurements, including length and weight, were obtained at birth at all sites, at 24 weeks in South Africa, and at 6 months in Nepal and Mali. The three trials are registered with ClinicalTrials.gov, numbers NCT01430689, NCT01034254, and NCT02465190.

Findings

10 002 women and 9800 liveborn infants were included. Pooled efficacy of maternal vaccination to prevent infant PCR-confirmed influenza up to 6 months of age was 35% (95% CI 19 to 47). The pooled estimate was 56% (28 to 73) within the first 2 months of life, 39% (11 to 58) between 2 and 4 months, and 19% (–9 to 40) between 4 and 6 months. In women, from enrolment during pregnancy to the end of follow-up at 6 months postpartum, the vaccine was 50% (95% CI 32–63) efficacious against PCR-confirmed influenza. Efficacy was 42% (12 to 61) during pregnancy and 60% (36 to 75) postpartum. In women vaccinated before 29 weeks gestational age, the estimated efficacy was 30% (–2 to 52), and in women vaccinated at or after 29 weeks, efficacy was 71% (50 to 83). Efficacy was similar in infants born to mothers vaccinated before or after 29 weeks gestation (34% [95% CI 12 to 51] vs 35% [11 to 52]). There was no overall association between maternal vaccination and low birthweight, stillbirth, preterm birth, and small for gestational age. At 6 months of age, the intervention and control groups were similar in terms of underweight (weight-for-age), stunted (length-for-age), and wasted (weight-for-length). Median centile change from birth to 6 months of age was similar between the intervention and the control groups for both weight and length.

Interpretation

The assessment of efficacy for women vaccinated before 29 weeks gestational age might have been underpowered, because the point estimate suggests that there might be efficacy despite wide CIs. Estimates of efficacy against PCR-confirmed influenza and safety in terms of adverse birth outcomes should be incorporated into any further consideration of maternal influenza immunisation recommendations.

Funding

Bill & Melinda Gates Foundation.

Safety and Immunogenicity of a Respiratory Syncytial Virus Fusion (F) Protein Nanoparticle Vaccine in Healthy Third-Trimester Pregnant Women and Their Infants

BACKGROUND

Respiratory syncytial virus (RSV) is the leading cause of infant lower respiratory tract disease and hospitalization worldwide.

METHODS

Safety and immunogenicity of RSV fusion (F) protein nanoparticle vaccine or placebo were evaluated in 50 healthy third-trimester pregnant women. Assessments included vaccine tolerability and safety in women and infants, and RSV-specific antibody measures in women before and after vaccination, at delivery and post partum.

RESULTS

The vaccine was well tolerated; no meaningful differences in pregnancy or infant outcomes were observed between study groups. RSV-specific antibody levels increased significantly among vaccine recipients, including responses competitive with well-described monoclonal antibodies specific for multiple RSV neutralizing epitopes. No significant antibody increase was seen among placebo recipients, although a shallow upward trend across the RSV season was noted. Transplacental antibody transfer was 90%-120% across assays for infants of vaccinated women. Women with an interval of ≥30 days between vaccination and delivery demonstrated higher placental antibody transfer rates than women with an interval <30 days. Half-lives of RSV-specific antibodies in infants approximated 40 days. There was no evidence of severe RSV disease in infants of vaccinated mothers.

CONCLUSIONS

Data from this phase 2 study support a maternal immunization strategy to protect infants from RSV disease.

CLINICAL TRIALS REGISTRATION

NCT02247726.

Vertically Transferred Immunity in Neonates: Mothers, Mechanisms and Mediators

Over the last years, an increasing number of outbreaks of vaccine-preventable infectious diseases has been reported. Besides elderly and immunocompromised individuals, newborns and small infants are most susceptible to infections, as their immune system is still immature. This vulnerability during infancy can be mitigated by the transplacental transfer of pathogen-specific antibodies and other mediators of immunity from mother to the fetus during pregnancy, followed postnatally by breast milk-derived immunity. Since this largely antibody-mediated passive immunity can prevent the newborn from infections, neonatal immunity depends strongly on the maternal concentration of respective specific antibodies during pregnancy. If titers are low or wane rapidly after birth, the protection transferred to the child may not be sufficient to prevent disease. Moreover, emerging concepts propose that mothers may transfer active immunity to the newborns via vertical transfer of pathogen-specific T cells. Overall, a promising strategy to augment and prolong neonatal immunity is to vaccinate the mother before or during pregnancy in order to boost maternal antibody concentrations or availability of specific T cells. Hence, a large number of pre-and postconceptional vaccine trials have been carried out to test and confirm this concept. We here highlight novel insights arising from recent research endeavors on the influence of prenatal maternal vaccination against pathogens that can pose a threat for newborns, such as measles, pertussis, rubella and influenza A. We delineate pathways involved in the transfer of specific maternal antibodies. We also discuss the consequences for children's health and long-term immunity resulting from an adjustment of prenatal vaccination regimes.

The Safety of Influenza and Pertussis Vaccination in Pregnancy in a Cohort of Australian Mother-Infant Pairs, 2012-2015: The FluMum Study

Background

Inactivated influenza vaccine (IIV) and pertussis vaccination are recommended in pregnancy. Limited safety data exist for women who received IIV vaccine during the first trimester of pregnancy or received both vaccines in pregnancy. We assessed adverse birth outcomes between vaccinated and unvaccinated pregnancies.

Methods

Among prospectively enrolled Australian "FluMum" participants (2012-2015), primary exposure was receipt and timing of IIV during pregnancy. Primary outcomes included preterm birth, low birthweight at term (LBWT), and small for gestational age (SGA). We compared birth outcomes for IIV in pregnancy with women unvaccinated in pregnancy using Cox proportional hazard ratios (HRs) with 95% confidence intervals (CIs). Adjusted HRs (aHRs) controlled for potential confounding variables. Sensitivity analyses were conducted in a subgroup of women who received pertussis vaccination during pregnancy to assess whether associations between IIV and adverse outcomes were maintained after adjusting for pertussis vaccination.

Results

Among 8827 participants in our study, women who received IIV in pregnancy did not have an elevated risk of an adverse birth outcome compared with unvaccinated pregnant women: preterm births (HR, 1.10 [95% CI, .92-1.31]; P = .28); LBWT (HR, 1.05 [95% CI, .76-1.44]; P = .77); or SGA (HR, 0.99 [95% CI, .86-1.15]; P = .94). Adjustment for pertussis vaccination during pregnancy yielded similar results: preterm births (aHR, 1.05 [95% CI, .82-1.34]; P = .69); LBWT (aHR, 0.81 [95% CI, .50-1.29]; P = .37); SGA (aHR, 0.92 [95% CI, .74-1.14]; P = .43). There was no evidence of elevated risk by trimester of IIV.

Conclusions

No significant associations were found between maternal IIV or pertussis vaccination in pregnancy and adverse birth outcomes, regardless of the trimester of pregnancy a vaccination was given compared to unvaccinated pregnancies.

Trivalent inactivated influenza vaccine (IIV3) during pregnancy and six-month infant development

OBJECTIVE

Despite recommendations by professional organizations that all pregnant women receive inactivated influenza vaccine, safety concerns remain a barrier. Our objective was to assess the effect of trivalent influenza vaccines (IIV3) during pregnancy on parent report 6-month infant development.

METHODS

We conducted a multi-site prospective birth cohort study during the 2010-2011 influenza season and followed pregnant women and their newborns through 6 months of age. Information on IIV3 during pregnancy was ascertained from the EHR and self-report. The Ages and Stages Questionnaire-3 (ASQ-3) was completed by the mother to assess 6-month infant neurodevelopment in five domains (communication, gross motor, fine motor, problem-solving, and personal adaptive skills). Scores for each domain above the cut-off point indicating typical development were categorized as "on schedule" while scores in the zones indicating the need for either monitoring or further assessment were categorized as "not on schedule". Multivariable logistic regression was conducted.

RESULTS

Of the 1225 infant-mother pairs, 65% received IIV3 during pregnancy. In bivariate analysis, infants of women who received IIV3 during pregnancy were moderately-less likely to need monitoring or further assessment in the personal social domain compared with infants of unvaccinated women (10.0% vs. 14.1%, p = 0.033; crude OR (cOR): 0.68(95%CI:0.48,0.97)). However, after controlling for potential confounders, the findings were no longer statistically significant (aOR:0.72,95%CI: 0.49,1.06,p = 0.46). No significant unadjusted or adjusted associations emerged in any other ASQ-3 domain.

CONCLUSION

There was no significant association between IIV3 exposure during pregnancy and 6-month infant development. Studies of IIV3 during pregnancy to assess longer-term developmental outcomes are indicated.

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.

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

Background

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

Methods

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

Results

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

Conclusions

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

Trivalent influenza vaccination randomized control trial of pregnant women and adverse fetal outcomes

•

A two-year randomized controlled trial of seasonal IIV3.

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Over 2000 mothers in South Africa, from March 2011 until post 2012 influenza season.

•

Birth outcomes investigated were fetal death, SGA, birth weight and prematurity.

•

Vaccine demonstrated no appreciable impact of maternal IIV3 immunization.

Introduction

The purpose of this study was to evaluate the association of influenza vaccine during pregnancy and adverse fetal outcomes. Preventing fetal death, low birth weight, small for gestational age birth and preterm birth are important potential effects of antenatal maternal influenza immunization for which there are conflicting data.

Materials and methods

A double-blind, randomized, placebo-controlled clinical trial of trivalent inactivated influenza vaccine was conducted in South Africa from March 2011 until after the 2012 influenza season when the infants born had reached the age of 24 weeks. Mothers were administered the vaccine or placebo during pregnancy at a gestation of 20 to 36 weeks. A comparison of rates of fetal death, low birth weight, small for gestational age birth, and preterm birth, between vaccinated and placebo groups was made. Fetal outcome differences between the groups were measured using Student’s t-tests, vaccine efficacy with 95% confidence intervals, and Poisson regression for incidence rates. All analyses except fetal death excluded mothers who were administered vaccine or placebo after 34 weeks gestational age.

Results

There were 2116 HIV-uninfected pregnant women age 18 to 38 years in the trial; 2005 infants were born to mothers where vaccine or placebo had been administered ≥ 14 days prior to delivery, and there were 6 miscarriages and 23 stillbirths. There was no significant vaccine efficacy (with [95% confidence interval]) on fetal death (−21.2% [−150.8, 41.4]), low birth weight (−11.1% [−42.3, 12.5]), small for gestational age birth (−9.9% [−35.6, 11.0]), or preterm birth (−21.3% [−60.5, 8.3]). Neither was vaccine efficacy demonstrated when the analysis was restricted to infants of mothers who were exposed to an influenza season (1832 outcomes available).

Conclusion

We did not find a beneficial effect of trivalent inactivated influenza vaccine during pregnancy on adverse fetal outcomes.

Coverage and determinants of influenza vaccine among pregnant women: a cross-sectional study

Background

Pregnant women are at increased risk of influenza-related complications. The World Health Organisation recommends influenza vaccination to this high-risk population as highest priority. However, achieving high influenza vaccine coverage among pregnant women remains challenging. We conducted a cross-sectional survey to estimate the coverage and determinants of influenza vaccination among pregnant women in Singapore.

Methods

Between September and November 2017, pregnant women aged ≥21 years were recruited at two public hospitals in Singapore. Participants completed an anonymous, self-administered online questionnaire assessing participants’ influenza vaccination uptake, knowledge of and attitudes towards influenza and the influenza vaccine, vaccination history, willingness to pay for the influenza vaccine, and external cues to vaccination. We estimated vaccine coverage and used multivariable Poisson models to identify factors associated with vaccine uptake.

Results

Response rate was 61% (500/814). Only 49 women (9.8, 95% Confidence Interval (CI): 7.3–12.7%) reported receiving the vaccine during their current pregnancy. A few misconceptions were identified among participants, such as the belief that influenza can be treated with antibiotics. The most frequent reason for not being vaccinated was lack of recommendation. Women who were personally advised to get vaccinated against influenza during pregnancy were 7 times more likely to be vaccinated (prevalence ratio (PR) = 7.11; 95% CI: 3.92–12.90). However, only 12% of women were personally advised to get vaccinated. Other factors associated with vaccine uptake were vaccination during a previous pregnancy (PR = 2.51; 95% CI: 1.54–4.11), having insurance to cover the cost of the vaccine (PR = 2.32; 95% CI: 1.43–3.76), and higher vaccine confidence (PR = 1.62; 95% CI: 1.30–2.01).

Conclusions

Influenza vaccination uptake among pregnant women in Singapore is low. There is considerable scope for improving vaccination coverage in this high-risk population through vaccination recommendations from healthcare professionals, and public communication targeting common misconceptions about influenza and influenza vaccines.

Electronic supplementary material

The online version of this article (10.1186/s12889-019-7172-8) contains supplementary material, which is available to authorized users.

Clinical Evaluations Have Low Sensitivity for Identifying Preterm Infants in a Clinical Trial in a Limited Resource Setting

Preterm birth is a primary outcome of interest in maternal vaccination trials but determination of gestational age is challenging in limited-resource settings. This study compares the New Ballard Score and fundal height measurements with the current standard of early ultrasound for sensitivity of predicting preterm birth. A trial of maternal influenza vaccination was conducted in Bamako, Mali. The New Ballard Score and fundal height were collected on 4038 infants born in the trial, ultrasound data were available for 1893 of those infants. New Ballard Score and fundal height were compared, consecutively, to all ultrasound results, early ultrasound results from the first trimester, and the date of last menstrual period for estimation of gestational age. Sensitivity of the New Ballard Score for identifying preterm infants was 0.33 compared with early ultrasound and 0.1 compared with the last menstrual period based estimates of gestational age. Sensitivity of low birth weight alone was 0.43 compared with early ultrasound. New Ballard Score estimated gestational age within 1 week of ultrasound more frequently than fundal height (53% compared with 7.6%, respectively) yet New Ballard Score identified few infants as preterm (1.8% vs 5.8% by early ultrasound), and was biased toward categorizing low birth weight infants and infants requiring hospitalization as preterm. New Ballard Score is not an ideal measure for identifying preterm births in low-resource settings. Despite the time and cost of training required for correct measurement of New Ballard Score, measurement of low birth weight alone performed better than New Ballard Score for identifying preterm infants.

Protective Effect of Maternal Influenza Vaccination on Influenza in Their Infants: A Prospective Cohort Study

Background

Infants <6 months of age are too young to receive influenza vaccine, despite being at high risk for severe influenza-related complications.

Methods

To examine the effectiveness of maternal influenza vaccination in preventing influenza in their infants, we conducted a prospective cohort study of 3441 infants born at participating hospitals before the 2013-2014 influenza season. At the time of recruitment, their mothers completed a questionnaire about influenza vaccination status for the 2013-2014 season. A follow-up survey was conducted after the end of the 2013-2014 season to collect information regarding influenza diagnosis and hospitalization among infants.

Results

During the 2013-2014 influenza season, 71 infants (2%) had influenza diagnosed, and 13 infants (0.4%) were hospitalized with influenza. Maternal influenza vaccination (especially prenatal vaccination) decreased the odds of influenza among infants. The effectiveness of prenatal vaccination was 61% (95% confidence interval, 16%-81%), whereas that of postpartum vaccination was 53% (-28%-83%). Although maternal influenza vaccination was also associated with a decreased odds of influenza-related hospitalization among infants, vaccine effectiveness (73%) did not reach statistical significance, owing to the limited number of infants hospitalized because of influenza.

Conclusions

The present findings indicated that pregnant women and postpartum women should receive influenza vaccination to protect their infants.

Why Should We Advocate Maternal Immunization?

Maternal vaccination provides a method for protecting the pregnant woman, fetus and neonate during a period when there is increased susceptibility to infectious diseases. A dynamic state of immune tolerance during pregnancy and the need to develop adaptive memory to a new foreign antigen-rich environment lead to windows of vulnerability to infection for the mother and neonate, respectively. Passive transfer of humoral immunity through the placenta and breast milk from the mother can bridge the gap in immunity for the neonate. Studies on boosting this natural process of antibody transfer have led to the recommendation for administering inactivated influenza, diphtheria, tetanus toxoid and acellular pertussis vaccines during pregnancy. Several new maternal vaccine candidates are on the horizon.

Clinical characteristics and outcomes of respiratory syncytial virus infection in pregnant women

OBJECTIVE

To describe the clinical presentation and laboratory diagnosis of pregnant women with respiratory syncytial virus (RSV) infection.

METHODS

Pregnant women in their second and third trimester were enrolled during the course of routine prenatal care visits when they were asymptomatic within the preceding two weeks (healthy controls) or when they reported symptoms of acute respiratory illness (ARI) of ≤7 days of duration (cases). Clinical outcomes were assessed at enrollment and two weeks after. Re-enrollment was allowed. Nasal-pharyngeal secretions were evaluated for respiratory pathogens by real-time reverse transcription polymerase chain reaction (PCR). Sera were tested for RSV-specific antibody responses by Western Blot, microneutralization assay, and palivizumab competitive antibody assay.

RESULTS

During the 2015-2016 respiratory virus season, 7 of 65 (11%) pregnant women with ARI at their initial enrollment and 8 of 77 (10%) pregnant women with ARI during the study period (initial or re-enrollment) had PCR-confirmed RSV infection. Four (50%) PCR-confirmed RSV ARI cases reported symptoms of a lower respiratory tract illness (LRTI), one was hospitalized. Combining PCR and serology data, the RSV attack rate at initial enrollment was 12% (8 of 65), and 13% (10 of 77) based on ARI episodes. Among healthy controls, 28 of 88 (32%) had a Western Blot profile suggestive of a recent RSV infection either in the prior and/or current season.

CONCLUSION

RSV had an attack rate of 10-13% among ambulatory pregnant women receiving routine prenatal care during the respiratory virus season. The serology results of healthy controls suggest a potentially higher attack rate. Future studies should be aware of the combined diagnostic strength of PCR and serology to identify RSV infection. As maternal RSV vaccine candidates are evaluated to protect young infants, additional priority should be placed on outcomes of pregnant women.

Prevention of Pediatric Respiratory Syncytial Virus Lower Respiratory Tract Illness: Perspectives for the Next Decade

The landscape of infant bronchiolitis and viral pneumonia may be altered by preventive interventions against respiratory syncytial virus under evaluation today. Pediatric wards in 2018 in developing countries may differ from those attended by future generation pediatricians who may not witness the packed emergency rooms, lack of available beds, or emergency situations that all physicians caring for children with RSV experience every year. In this review, we describe and discuss different prevention strategies under evaluation to protect pediatric patients. Then, we outline a number of potential challenges, benefits, and concerns that may result from successful interventions after licensure.

H1N1 Infection in Pregnancy; A Retrospective Study of Feto-Maternal Outcome and Impact of the Timing of Antiviral Therapy

Background and Objective

H1N1 infection carries an increased risk in pregnancy. Our aim was to study the feto-maternal outcome and the effect of early initiation of therapy.

Methods

This is a retrospective descriptive study. Confirmed infected cases were included. Maternal age, parity, gestational age at diagnosis, presenting symptoms, the time between presentation and starting therapy, ICU admission, and maternal and perinatal outcome were evaluated.

Results

Nineteen confirmed patients were included. Most patients are 31 years old or more. Multiparous patients were 73.68%, and 57.89% were in the third trimester. Most of our patients presented with cough, fever, and chills. Two patients were admitted to the ICU. One of them was a case of maternal mortality. 42.10% of patients were started on therapy only one day after the clinical onset of symptoms. 26.31% delivered before 37 completed weeks. 73.68% delivered beyond term. Around one third delivered vaginally. 45% of babies weighed more than 3 kg. Four babies weighed less than 2 kg. Ninety percent had APGAR scores more than 8 at 1 and 5 minutes after delivery. Twenty-five percent were admitted to the NICU with no neonatal mortalities.

Conclusions

H1N1 influenza A infection in pregnancy is associated with adverse maternal and perinatal outcomes. Medical and public awareness, low threshold for testing suspected pregnant patients, very early initiation of antiviral therapy, and a multidisciplinary approach in our series decreased the overall adverse effects of this infection.

Knowledge about influenza and adherence to the recommendations for influenza vaccination of pregnant women after an educational intervention in Greece

Pregnant women and young infants are at increased risk for influenza-associated severe disease, complications and hospitalizations. In Greece influenza vaccination during pregnancy remains extremely low. We studied the knowledge about influenza and the adherence to the recommendations for influenza vaccination of pregnant women following an educational intervention in a large maternity hospital. A standardized questionnaire was used. A knowledge score was calculated for each woman. A total of 304 pregnant women were studied [mean age: 31.5 years (standard deviation (SD): 5.4 years), mean gestational age: 27.8 weeks (SD: 9.6 weeks)]. Their mean knowledge score was 87%. Sixty pregnant women (19.5%) were vaccinated against influenza at a mean gestational age of 24.6 weeks (SD: 7.5 weeks). Multiple regression analysis revealed that previous influenza vaccination and information about the need to get vaccinated were the only significant factors associated with an increased probability for influenza vaccination during pregnancy (47% versus 17% in women with and without a history of influenza vaccination in the past, respectively; odds ratio = 3.6; p-value = 0.016, and 32% versus 4% in women informed compared to those uninformed about the need for vaccination during pregnancy, respectively; odds ratio = 17.8; p-value<0.001). Seventy women provided a reason for refusing influenza vaccination. "Fear of adverse events" (for them or the fetus) was the prevalent reason for refusing influenza vaccination (19 women; 27%), followed by the statements "influenza vaccination is not necessary" (13; 18.5%) and "not at risk to get influenza" (9; 13%). In conclusion, an educational intervention was associated with an influenza vaccination rate of 19.5% among pregnant women compared to <2% the past years. In order to improve vaccine uptake by pregnant women and protect them and their babies, more intensified interventions should be explored.

Vitamin A Supplementation during Pregnancy Enhances Pandemic H1N1 Vaccine Response in Mothers, but Enhancement of Transplacental Antibody Transfer May Depend on When Mothers Are Vaccinated during Pregnancy

Background

In the growing embryo, the vitamin A requirement is tightly regulated. Maternal vitamin A deficiency during pregnancy may alter maternal immune function to accommodate the fetus.

Objective

Our primary objective was to determine the effect of oral vitamin A supplementation (VAS) during pregnancy and until 6 mo postpartum on pandemic H1N1-vaccine responses in mothers and their infants at 6 mo of age.

Methods

In this randomized controlled clinical trial, pregnant women (n = 112) during the second trimester (mean ± SD: 14 ± 1 wk) were assigned to receive either an oral dose of 10,000 IU vitamin A or placebo weekly until 6 mo postpartum. During the third trimester, mothers received a single dose of inactivated pandemic H1N1-influenza vaccine. Hemagglutination-inhibition (HAI) titer was measured in cord, infant, and maternal blood samples. Multivariate regressions with adjustments were used for data analysis.

Results

Seventy-six percent of women had low plasma retinol concentrations (<1.05 μmol/L) in their second trimester. VAS of mothers increased vitamin A concentrations in cord blood by 21.4% and in colostrum by 40.7%. At 6 mo postpartum, women in the vitamin A group had 38.7% higher HAI titers and a higher proportion of HAI titer of ≥1:40 of the cutoff compared with the placebo group. A total of 54.5% of infants had an HAI titer ≥1:40 at 6 mo of age, but there was no difference in HAI titer in infants between groups. Overall, HAI in cord blood did not differ between groups, but in the placebo group, cord blood HAI was negatively associated with maternal "vaccination-to-delivery intervals" (rs = -0.401; P = 0.5), and maternal VAS increased cord blood HAI 6-fold if antenatal immunization was administered ≥10 wk before delivery.

Conclusions

In a community with low vitamin A status, weekly maternal VAS during pregnancy and postpartum increases the breast-milk vitamin A concentration and enhances prenatal H1N1-vaccine responses in mothers, but the benefits of maternal VAS in transplacental antibody transfer may depend on the time of gestation when mothers were vaccinated. This trial was registered at clinicaltrials.gov as NCT00817661.

Prioritization of risk groups for influenza vaccination in resource limited settings - A case study from South Africa

BACKGROUND

Due to competing health priorities, low- and middle-income countries (LMIC) may need to prioritize between different influenza vaccine risk groups. Risk group prioritization may differ in LMIC based upon programmatic feasibility, country-specific prevalence of risk conditions and influenza-associated morbidity and mortality.

METHODS

In South Africa, we collected local disease burden data (both published and unpublished) and published vaccine efficacy data in risk groups and healthy adults. We used these data to aid policy makers with risk group prioritization for influenza vaccination. We used the following formula to assess potential vaccine averted disease in each risk group: rate of influenza-associated hospitalization (or death) per 100,000 population * influenza vaccine efficacy (VE). We further estimated the cost per hospital day averted and the cost per year of life saved by influenza vaccination.

RESULTS

Pregnant women, HIV-infected adults, and adults and children with tuberculosis disease had among the highest estimates of hospitalizations averted per 100,000 vaccinated and adults aged 65 years and older had the highest estimated deaths averted per 100,000 vaccinated. However, when assessing both the cost per hospital day averted (range: USD148-1,344) and the cost per year of life saved (range: USD112-1,230); adults and children with TB disease, HIV-infected adults and pregnant women had the lowest cost per outcome averted.

DISCUSSION

An assessment of the potential disease outcomes averted and associated costs may aid policymakers in risk group prioritization for influenza vaccination.

Risk of pregnancy complications and adverse birth outcomes after maternal A(H1N1)pdm09 influenza: a Norwegian population-based cohort study

Background

The effects of maternal influenza infection on the fetus remain unclear. We studied mild influenza and influenza antibodies in relation to birth weight and risks of pre-eclampsia, preterm birth (PTB), and small for gestational age (SGA) birth among the unvaccinated participants in the Norwegian Influenza Pregnancy Cohort.

Methods

Pregnant women attending a routine ultrasound were recruited from four hospitals in Norway shortly after the 2009 A(H1N1) pandemic. The present study was restricted to unvaccinated participants who were pregnant during the pandemic. Information on the participants was obtained through questionnaires and linkage with national registries. Maternal blood samples were collected at delivery. Women with laboratory-confirmed A(H1N1)pdm09 influenza, a clinical diagnosis of influenza, or self-reported influenza during the pandemic were classified as having had influenza. A(H1N1)pdm09-specific antibodies in serum were detected with the hemagglutination-inhibition assay. Detection of antibodies was considered an indicator of infection during the pandemic in the unvaccinated participants. Odds ratios were estimated with logistic regression. Quantile regression was used to estimate differences in the distribution of birth weight.

Results

Among the 1258 women included in this study, there were 37 cases of pre-eclampsia, 41 births were PTB, and 103 births were SGA. 226 women (18.0%) had influenza during the pandemic. The majority of cases did not receive medical care, and only a small proportion (1.3%) of the cases were hospitalized. Thus, the cases consisted primarily of women with mild illness. No significant associations between influenza and risk of pre-eclampsia, PTB, or SGA birth were observed. Detection of A(H1N1)pdm09-specific antibodies was associated with a lower 10th percentile of birth weight, β = − 159 g (95% CI − 309, − 9).

Conclusions

Mild influenza illness during pregnancy was not associated with increased risk of pre-eclampsia, PTB or SGA birth. However, influenza infection during pregnancy may reduce the birth weight of the smallest children.

Active prophylaxis for respiratory syncytial virus: current knowledge and future perspectives

Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children but represents also an important cause of morbidity in adults, particularly in the elderly and immunocompromised persons. Despite its global impact on human health, no effective treatment is available except for supportive care and no safe vaccine has been licensed yet. Vaccine development has been hindered by several factors including vaccine enhanced disease associated with formalin-inactivated RSV vaccine, ethical concerns and lack of consensus concerning the most appropriate target antigen. In this review, we analyze history of RSV vaccine and current approaches for preventing RSV including live-attenuated, vector-based, subunit, nucleic acid-based, particle-based vaccines and we debate about concerns on target population, correlates of protection and obstacles that are slowing the progress toward a successful RSV vaccination strategy.

Infections in Pregnancy and the Role of Vaccines

Pregnant women are at risk for infection and may have significant morbidity or mortality. Influenza, pertussis, zika, and cytomegalovirus produce mild or asymptomatic illness in the mother, but have profound implications for her fetus. Maternal immunization can prevent or mitigate infections in pregnant women and their infants. The Advisory Committee of Immunization Practices recommends 2 vaccines during pregnancy: inactivated influenza, and tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis during pregnancy. The benefits of MMR, varicella, and other vaccines are reviewed. Novel vaccine studies for use during pregnancy for prevention of illness are explored.

Experience and challenges on influenza and pertussis vaccination in pregnant women

Young infants contribute to relatively high burden of vaccine-preventable diseases, including infections by influenza virus and Bordetella pertussis. Vaccination of pregnant women can enhance transplacental transfer of protective antibody to the fetus and protect the infant against disease during the first few months of life.

Pregnant women are a priority group for seasonal influenza vaccination, due to third-trimester pregnancy being a risk-factor for severe influenza illness. Furthermore, randomized controlled trials confirmed that influenza vaccination during pregnancy confers protection against influenza-confirmed illness in the women, and their infants up to 3 months of age; and is also associated with 20% reduction in all-cause pneumonia among young-infants. Maternal influenza vaccination might also reduce the risk of low-birth weight, preterm births, and stillbirths however, data on this is conflicting.

Vaccination of pregnant women with acellular pertussis vaccines reduces pertussis in their young infants by up to 93%. The increase in specific pertussis antibody among the infants born to vaccinated women might, however, interfere with the active pertussis vaccination of the infant following the primary series of vaccines. The clinical implication of this is yet to be ascertained, particularly since immune responses following the booster vaccine are unaffected.

Vaccination of pregnant women with inactivated influenza vaccine and acellular pertussis vaccine have been demonstrated to confer protection to their young infants, and warrants consideration for inclusion into public health immunization programs, including in low and middle income countries.

Impact of Timing of Influenza Vaccination in Pregnancy on Transplacental Antibody Transfer, Influenza Incidence, and Birth Outcomes: A Randomized Trial in Rural Nepal

Background

Maternal influenza vaccination protects mothers and their infants in low resource settings, but little is known about whether the protection varies by gestational age at vaccination.

Methods

Women of childbearing age in rural southern Nepal were surveilled for pregnancy, consented and randomized to receive maternal influenza vaccination or placebo, with randomization stratified on gestational age (17-25 or 26-34 weeks). Enrollment occurred in 2 annual cohorts, and vaccinations occurred from April 2011 through September 2013.

Results

In sum, 3693 women consented and enrolled, resulting in 3646 live births. Although cord blood antibody titers and the rise in maternal titers were generally greater when women were vaccinated later in pregnancy, this was not statistically significant. The incidence risk ratio (IRR) for maternal influenza in pregnancy through 6 months postpartum was 0.62 (95% confidence interval [CI]: 0.35, 1.10) for those vaccinated 17-25 weeks gestation and 0.89 (95% CI: 0.39, 2.00) for those 26-34 weeks. Infant influenza IRRs were 0.73 (95% CI: 0.51, 1.05) for those whose mothers were vaccinated earlier in gestation, and 0.63 (95% CI: 0.37, 1.08) for those later. Relative risks (RR) for low birthweight were 0.83 (95% CI: 0.71, 0.98) and 0.90 (95% CI: 0.72, 1.12) for 17-25 and 26-34 weeks gestation at vaccination, respectively. IRRs did not differ for small-for-gestational age or preterm. No RRs were statistically different by timing of vaccine receipt.

Conclusions

Vaccine efficacy did not vary by gestational age at vaccination, making maternal influenza immunization programs easier to implement where women present for care late in pregnancy.

Clinical Trials Registration

NCT01034254.

No. 357-Immunization in Pregnancy

OBJECTIVE

To review the evidence and provide recommendations on immunization in pregnancy.

OUTCOMES

Outcomes evaluated include effectiveness of immunization and risks and benefits for mother and fetus.

EVIDENCE

The Medline and Cochrane databases were searched for articles published up to January 2017 on the topic of immunization in pregnancy.

VALUES

The evidence obtained was reviewed and evaluated by the Infectious Diseases Committee of the SOGC under the leadership of the principal authors, and recommendations were made according to guidelines developed by the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Implementation of the recommendations in this guideline should result in more appropriate immunization of pregnant and breastfeeding women, decreased risk of contraindicated immunization, and better disease prevention.

RECOMMENDATIONS

Clinician perspectives on strategies to improve patient maternal immunization acceptability in obstetrics and gynecology practice settings

Pregnancy is an ideal time to communicate with women about vaccines for themselves and their infants, yet maternal immunization rates remain suboptimal. This study aimed to identify clinic, provider, and staff-related attributes and facilitators to be utilized for a comprehensive vaccine intervention in ob-gyn clinical settings. We conducted in-depth interviews with 24 providers, both healthcare providers (e.g., physicians, nurse practitioners, midwives) and practice managers, from urban and suburban ob-gyn practices in Georgia and Colorado about their immunization attitudes, practices, and patient experiences. Qualitative analyses included Pearson correlation tests to evaluate patterns and relationships within the data to determine themes. Six major themes emerged: 1) strong provider "buy in" for maternal immunization; 2) the supporting role of clinical/interpersonal cues for vaccine promotion; 3) varying provider-patient communication approaches and its influence on maternal and pediatric uptake; 4) an urgent need for a designated office immunization champion; 5) reimbursement and practice implementation challenges; and 6) region differences in attitudes and values toward maternal immunization. Although providers expressed strong support for maternal immunization practices and offered environmental cues for vaccine promotion, practices often lacked a designated, structured role for an immunization champion equipped to manage delicate conversations with patients. The findings reflect needs for immunization champion identification, training, and support, along with best practices guidelines to improve coordination of vaccine promotion and delivery efforts in ob-gyn provider offices. Additionally, provider training on communication approaches to enhance acceptance and uptake of maternal vaccines is warranted.

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%).