Maternal immunization: where are we now and how to move forward?

Acceptance and uptake of vaccines against tetanus, influenza, pertussis, and COVID-19 among pregnant and postpartum women in low- and middle-income countries: a systematic review and meta-analysis protocol

BACKGROUND

Pregnant women, fetuses, and neonates are particularly vulnerable to vaccine-preventable diseases (VPDs). These VPDs are associated with high morbidity and mortality among expectant mothers and their fetuses and neonates. Vaccination during pregnancy can protect the expectant mother from VPDs to which she may be especially vulnerable while pregnant. In addition, the passive transfer of maternal neutralizing immunoglobulin G (IgG) and secretory immunoglobulin A (IgA) also protects the fetus against congenital infections and may further protect the neonate from infection during the first few months of life. Despite this, coverage of recommended maternal vaccines remains suboptimal globally, especially in resource-constrained settings. Determinants of vaccine acceptance and uptake are frequently understudied in low- and middle-income countries (LMICs) and among specific groups such as pregnant and postpartum women. This proposed systematic review will assess the acceptance and uptake of vaccines against tetanus, influenza, pertussis, and COVID-19 among pregnant and postpartum women in LMICs.

METHODS

A Boolean search strategy employing common and medical subject heading (MeSH) terms for tetanus, influenza, pertussis, and COVID-19 vaccines, as well as vaccine acceptance, hesitancy, together with uptake, pregnancy, and postpartum, will be used to search electronic databases for relevant literature published between 2009 and 2024. Only studies conducted in LMICs that investigated determinants of acceptance, hesitancy, and uptake of tetanus, influenza, pertussis, and COVID-19 vaccines among pregnant and postpartum women will be eligible for inclusion in the review. The quality and the risk of bias of all eligible full-text articles will be assessed using the Joanna Briggs Institute's (JBI) critical appraisal tools.

DISCUSSION

This protocol proposes a systematic review and meta-analysis that aims to assess the uptake of maternal vaccines and to systematically appraise and quantify determinants of the acceptance and uptake of recommended vaccines during pregnancy and postpartum in LMICs. A better understanding of these factors and how they influence maternal vaccine decision-making will enable public health practitioners as well as global and national policymakers to design more effective interventions as we look towards expanding the scope and reach of maternal immunization programs.

Vaccine value profile for invasive non-typhoidal Salmonella disease

Invasive non-typhoidal Salmonella (iNTS) disease is an under-recognized high-burden disease causing major health and socioeconomic issues in sub-Saharan Africa (sSA), predominantly among immune-naïve infants and young children, including those with recognized comorbidities such as HIV infection. iNTS disease is primarily caused by Salmonella enterica serovar Typhimurium sequence type (ST) 313 and 'African-restricted clades' of Salmonella Enteritidis ST11 that have emerged across the African continent as a series of epidemics associated with acquisition of new antimicrobial resistance. Due to genotypes with a high prevalence of antimicrobial resistance and scarcity of therapeutic options, these NTS serovars are designated by the World Health Organization as a priority pathogen for research and development of interventions, including vaccines, to address and reduce NTS associated bacteremia and meningitis in sSA. Novel and traditional vaccine technologies are being applied to develop vaccines against iNTS disease, and the results of the first clinical trials in the infant target population should become available in the near future. The "Vaccine Value Profile" (VVP) addresses information related predominantly to invasive disease caused by Salmonella Enteritidis and Salmonella Typhimurium prevalent in sSA. Information is included on stand-alone iNTS disease candidate vaccines and candidate vaccines targeting iNTS disease combined with another invasive serotype, Salmonella Typhi, that is also common across sSA. Out of scope for the first version of this VVP is a wider discussion on either diarrheagenic NTS disease (dNTS) also associated with Salmonella Enteritidis and Salmonella Typhimurium or the development of a multivalent Salmonella vaccines targeting key serovars for use globally. This VVP for vaccines to prevent iNTS disease is intended to provide a high-level, holistic assessment of the information and data that are currently available to inform the potential public health, economic, and societal value of pipeline vaccines and vaccine-like products. Future versions of this VVP will be updated to reflect ongoing activities such as vaccine development strategies and a "Full Vaccine Value Assessment" that will inform the value proposition of an iNTS disease vaccine. This VVP was developed by a working group of subject matter experts from academia, non-profit organizations, public private partnerships, and multi-lateral organizations, and in collaboration with stakeholders from the World Health Organization African Region. All contributors have extensive expertise on various elements of the iNTS disease VVP and collectively aimed to identify current research and knowledge gaps. The VVP was developed using only existing and publicly available information.

Effect of COVID-19 infection on pregnant women in plateau regions

OBJECTIVE

The present study aims to explore the effect of COVID-19 infection on pregnant women in plateau regions.

STUDY DESIGN

Data from 381 pregnant women infected with COVID-19 who underwent prenatal examination or treatment at Women and Children's Hospital of Tibet Autonomous Region between January 2020 and December 2022 and 314 pregnant women not infected with COVID-19 were retrospectively collected.

METHODS

The study participants were divided into an infected and non-infected group according to whether they were infected with COVID-19. Basic information (ethnicity, age, body mass index and gestational age [GA]), vaccination status, intensive care unit (ICU) admission and delivery outcomes were compared. Binary logistic regression was used to analyse the influencing factors of ICU admission.

RESULTS

The results revealed significant differences in the GA, vaccination rate, blood pressure, partial pressure of oxygen, white blood cell (WBC) count, ICU admission rate, preeclampsia rate, forearm presentation rate, thrombocytopenia rate, syphilis infection rate and placental abruption rate between the two groups (P < 0.05). A univariate analysis showed that COVID-19 infection, hepatitis B virus infection, the WBC count and hypoproteinaemia were risk factors for ICU admission. The results of the multivariate analysis of the ICU admission of pregnant women showed that COVID-19 infection (odds ratio [OR] = 4.271, 95 % confidence interval [CI]: 3.572-5.820, P < 0.05) was a risk factor for ICU admission and the WBC count (OR = 0.935, 95 % CI: 0.874-0.947, P < 0.05) was a protective factor for ICU admission.

CONCLUSION

Pregnant women are vulnerable to the adverse consequences of COVID-19 infection, and public health measures such as vaccination are needed to protect this population subgroup.

RSV Prefusion F Protein-Based Maternal Vaccine - Preterm Birth and Other Outcomes

BACKGROUND

Vaccination against respiratory syncytial virus (RSV) during pregnancy may protect infants from RSV disease. Efficacy and safety data on a candidate RSV prefusion F protein-based maternal vaccine (RSVPreF3-Mat) are needed.

METHODS

We conducted a phase 3 trial involving pregnant women 18 to 49 years of age to assess the efficacy and safety of RSVPreF3-Mat. The women were randomly assigned in a 2:1 ratio to receive RSVPreF3-Mat or placebo between 24 weeks 0 days and 34 weeks 0 days of gestation. The primary outcomes were any or severe medically assessed RSV-associated lower respiratory tract disease in infants from birth to 6 months of age and safety in infants from birth to 12 months of age. After the observation of a higher risk of preterm birth in the vaccine group than in the placebo group, enrollment and vaccination were stopped early, and exploratory analyses of the safety signal of preterm birth were performed.

RESULTS

The analyses included 5328 pregnant women and 5233 infants; the target enrollment of approximately 10,000 pregnant women and their infants was not reached because enrollment was stopped early. A total of 3426 infants in the vaccine group and 1711 infants in the placebo group were followed from birth to 6 months of age; 16 and 24 infants, respectively, had any medically assessed RSV-associated lower respiratory tract disease (vaccine efficacy, 65.5%; 95% credible interval, 37.5 to 82.0), and 8 and 14, respectively, had severe medically assessed RSV-associated lower respiratory tract disease (vaccine efficacy, 69.0%; 95% credible interval, 33.0 to 87.6). Preterm birth occurred in 6.8% of the infants (237 of 3494) in the vaccine group and in 4.9% of those (86 of 1739) in the placebo group (relative risk, 1.37; 95% confidence interval [CI], 1.08 to 1.74; P = 0.01); neonatal death occurred in 0.4% (13 of 3494) and 0.2% (3 of 1739), respectively (relative risk, 2.16; 95% CI, 0.62 to 7.56; P = 0.23), an imbalance probably attributable to the greater percentage of preterm births in the vaccine group. No other safety signal was observed.

CONCLUSIONS

The results of this trial, in which enrollment was stopped early because of safety concerns, suggest that the risks of any and severe medically assessed RSV-associated lower respiratory tract disease among infants were lower with the candidate maternal RSV vaccine than with placebo but that the risk of preterm birth was higher with the candidate vaccine. (Funded by GlaxoSmithKline Biologicals; ClinicalTrials.gov number, NCT04605159.).

Quantitative Analysis of the Instant and Persistent Inhibition Effects of Maternal Poliovirus Antibodies on the Immune Response in a Phase IV Trial of a Sabin Strain-Based Inactivated Poliovirus Vaccine

BACKGROUND

An inactivated poliomyelitis vaccine made from Sabin strains (sIPVs) has widely been used in China since 2015. However, the quantitative data on the instant and persistent inhibition effects of maternal poliovirus antibodies on the immune response to sIPV priming and booster vaccination have not been available yet.

OBJECTIVE

In this study, we aim to explore and quantify the instant and persistent inhibition effect of maternal poliovirus antibodies on the immune response elicited by sIPV primary and booster vaccination.

METHODS

The immunogenicity data consisting of the days 0 and 30 after the prime and booster vaccination of the sIPV in a phase IV trial were pooled for a quantitative analysis of the inhibition effect of maternal poliovirus antibody. The geometric mean ratio (GMR) was calculated using linear regression models, representing that every 2-fold higher maternal poliovirus antibody titer may result in a (1-GMR) lower postimmunization antibody titer.

RESULTS

The GMRs for poliovirus types 1, 2, and 3 were 0.79 (0.77-0.82), 0.85 (0.81-0.89), and 0.87 (0.83-0.91) at 30 days after the priming series, 0.86 (0.83-0.89), 0.81 (0.76-0.85), and 0.86 (0.80-0.93) at one year after the priming series, and 0.96 (0.94-0.99), 0.89 (0.86-0.93), and 0.98 (0.93-1.03) at 30 days after the booster dose. The inhibition effect continued to exist until the booster dose 1 year later, and such a persistent inhibition effect was almost attenuated for poliovirus types 1 and 3, and partly reduced for type 2 at 30 days after the booster dose.

CONCLUSION

A wider interval between the four sIPV doses might be a consideration for reducing the effect of maternal antibodies and subsequently eliciting and maintaining higher antibody levels to protect against poliovirus transmission and infection at the final stage of polio eradication in the global world. This study's clinical trial registry number is NCT04224519.

Maternal Tdap and influenza vaccination uptake 2017-2021 in the United States: Implications for maternal RSV vaccine uptake in the future

BACKGROUND

Assessment of maternal vaccine coverage is important for understanding and quantifying the impact of currently recommended vaccines as well as modeling the potential impact of future vaccines. However, existing data lack detail regarding uptake according to week of gestational age (wGA). Such granularity is valuable for more accurate estimation of vaccine impact.

OBJECTIVE

To summarize contemporary maternal Tdap vaccination uptake, overall, yearly, and by wGA, and maternal influenza vaccination uptake, overall, by influenza observation year, immunization month, and delivery month, in the US.

METHODS

Female patients 18-49 years of age with a pregnancy resulting in a live born infant (i.e., delivery) between 2017 and 2021 were selected from the Optum electronic health records (EHRs) database. Recently published gestational age algorithms were utilized to estimate wGA.

RESULTS

Of 1,021,260 deliveries among 886,660 women between 2017-2021, 55.1% had Tdap vaccination during pregnancy; vaccine coverage varied slightly by year (2017: 56.6%; 2018: 55.2%; 2019: 55.2%; 2020: 54.7%; 2021: 52.1%). Most (64.4%) maternal Tdap vaccinations occurred 27-32 wGA; 79.5% occurred during the entire 10-week recommended vaccination window (27-36 wGA). In the evaluation of influenza vaccination uptake (n=798,113 deliveries; 714,841 women), 33.5% of deliveries had influenza vaccination during influenza observation years 2017-2021, most (73.0%) of which occurred during influenza peak activity months (October-January) with approximately one-quarter (27.0%) of vaccinations having occurred during the off-peak months, mostly in September.

CONCLUSIONS

In this large contemporary analysis of EHR data, uptake of Tdap vaccination during pregnancy was consistent with previously published estimates; notably, most vaccination occurred early in the recommended 27-36 wGA window. Maternal influenza vaccination uptake largely correlated with peak influenza activity months and not gestational age. These study findings may have important implications for estimating the potential uptake and impact of future maternal vaccines.

Interventions to Improve Knowledge, Attitudes, and Uptake of Recommended Vaccines during Pregnancy and Postpartum: A Scoping Review

Tetanus, pertussis, influenza, and COVID-19 vaccines are recommended for the prevention of related morbidity and mortality during pregnancy and postpartum. Despite the established benefits of vaccination for prenatal and postnatal women, maternal vaccination is not universally included in routine antenatal programs, especially in low- and middle-income countries. Furthermore, the uptake of recommended vaccines among pregnant and postpartum women remains below optimum globally. This review aimed to map the evidence on interventions to improve knowledge, attitudes, and uptake of recommended vaccines among pregnant and postpartum women. We conducted a comprehensive and systematic search for relevant literature in PubMed, Scopus, Web of Science, EBSCOhost, and Google Scholar. Overall, 29 studies published between 2010 and 2023 were included in this review. The majority (n = 27) of these studies were from high-income countries. A total of 14 studies focused on the influenza vaccine, 6 on the Tdap vaccine, 8 on both influenza and Tdap vaccines, and only one study on the COVID-19 vaccine. Patient-centered interventions predominated the evidence base (66%), followed by provider-focused (7%), health system-focused (10%), and multilevel interventions (17%). Overall, the effect of these interventions on knowledge, attitudes, and uptake of maternal vaccines was variable.

Are maternal vaccines effective and safe for mothers and infants? A systematic review and meta-analysis of randomised controlled trials

INTRODUCTION

Maternal vaccination is a promising strategy to reduce the burden of vaccine-preventable diseases for mothers and infants. We aimed to provide an up-to-date overview of the efficacy and safety of all available maternal vaccines.

METHODS

We searched PubMed, Embase, CENTRAL and ClinicalTrials.gov on 1 February 2022, for phase III and IV randomised controlled trials (RCTs) that compared maternal vaccination against any pathogen with placebo or no vaccination. Primary outcomes were laboratory-confirmed or clinically confirmed disease in mothers and infants. Secondary safety outcomes included intrauterine growth restriction, stillbirth, maternal death, preterm birth, congenital malformations and infant death. Random effects meta-analysis were used to calculate pooled risk ratio's (RR). Quality appraisal was performed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE).

RESULTS

Six RCTs on four maternal vaccines, influenza, tetanus, diphtheria and pertussis (Tdap), pneumococcal and respiratory syncytial virus (RSV) were eligible. The overall risk of bias and certainty of evidence varied from low to high. Maternal influenza vaccination significantly reduced the number of laboratory-confirmed influenza cases (RR 0.58, 95% CI 0.42 to 0.79, event rate 57 vs 98, 2 RCTs, n=6003, I2=0%), and clinically confirmed influenza cases in mothers (RR 0.88, 95% CI 0.78 to 0.99, event rate 418 vs 472, 2 RCTs, n=6003, I2=0%), and laboratory-confirmed influenza in infants (RR 0.66, 95% CI 0.52 to 0.85, event rate 98 vs 148, 2 RCTs, n=5883, I2=0%), although this was not significant for clinically confirmed influenza in infants (RR 0.99, 95% CI 0.94 to 1.05, event rate 1371 vs 1378, 2 RCTs, n=5883, I2=0%). No efficacy data were available on maternal Tdap vaccination. Maternal pneumococcal vaccination did not reduce laboratory-confirmed and clinically confirmed middle ear disease (RR 0.49, 95% CI 0.24 to 1.02, event rate 9 vs 18, 1 RCT, n=133 and RR 0.88 95% CI 0.69 to 1.12, event rate 42 vs 47, 1 RCT, n=133, respectively), and clinically confirmed lower-respiratory tract infection (LRTI) (RR 1.08, 95% CI 0.82 to 1.43, event rate 18 vs 34, 1 RCT, n=70) in infants. Maternal RSV vaccination did not reduce laboratory-confirmed RSV LRTI in infants (RR 0.75, 95% CI 0.56 to 1.01, event rate 103 vs 71, 1 RCT, n=4527). There was no evidence of a significant effect of any of the maternal vaccines on the reported safety outcomes.

CONCLUSIONS

The few RCTs with low event rates suggest that, depending on the type of maternal vaccine, the vaccine might effectively prevent disease and within its size does not show safety concerns in mothers and infants.

PROSPERO REGISTRATION NUMBER

CRD42021235115.

Safety and Immunogenicity of an Investigational Respiratory Syncytial Virus Vaccine (RSVPreF3) in Mothers and Their Infants: A Phase 2 Randomized Trial

BACKGROUND

In a phase 1/2 study, a maternal respiratory syncytial virus vaccine candidate (RSVPreF3) demonstrated an acceptable safety profile and efficiently increased RSV-specific humoral immune responses in non-pregnant women.

METHODS

In this phase 2 observer-blind, placebo-controlled, randomized clinical trial (NCT04126213), the safety of RSVPreF3 (60 or 120 µg), administered during late second or third trimester, was evaluated in 213 18- to 40-year-old healthy pregnant women through 6 months postdelivery and their offspring through infancy; immunogenicity was evaluated through day 43 postdelivery and day 181 postbirth, respectively.

RESULTS

RSVPreF3 was well tolerated. No pregnancy-related or neonatal adverse events of special interest were considered vaccine/placebo related. In the 60 and 120 µg RSVPreF3 groups: (1) neutralizing antibody (nAb) titers in mothers increased 12.7- and 14.9-fold against RSV-A and 10.6- and 13.2-fold against RSV-B, respectively, 1 month postvaccination and remained 8.9-10.0-fold over prevaccination at day 43 postdelivery; (2) nAb titers were consistently higher compared to placebo recipients; (3) placental transfer ratios for anti-RSVPreF3 antibodies at birth were 1.62 and 1.90, respectively, and (4) nAb levels in infants were highest at birth and declined through day 181 postbirth.

CONCLUSIONS

RSVPreF3 maternal vaccination had an acceptable safety risk profile and induced robust RSV-specific immune responses with successful antibody transfer to their newborns.

CLINICAL TRIALS REGISTRATION

NCT04126213.

Vertical transmission and maternal passive immunity post-SARS-CoV-2

Since 2020, the highly contagious nature and various transmission routes of SARS-CoV-2 have rendered the pandemic interminable. Vertical transmission (VT) through the placenta and breast milk, which is frequent for certain virus types, is thought to exist for SARS-CoV-2 and is hypothesized by many researchers. Conversely, antibodies are produced to counteract the effect of viruses. Since newborns' immunologic system cannot produce proper antibodies, maternal antibodies are usually transferred from mother to infant/fetus to meet the need. This theory leads to the hypothesis of transmission of antibodies through the placenta and breast milk following SARS-CoV-2 infection or vaccination. This paper further discusses these hypotheses, considering consequences of fetus/infant harm versus benefit.

Impact of maternal whole-cell or acellular pertussis primary immunization on neonatal immune response

With the introduction of pertussis immunization for pregnant women in many countries, there has been renewed interest in the impact of whole-cell pertussis vaccine (wP) versus acellular vaccine (aP) on disease control, particularly regarding the best approach for priming. To gather evidence on this topic, we analyzed the impact of aP or wP priming on aP vaccination during pregnancy (aPpreg) in mice. Two-mother vaccination schemes were employed (wP-wP-aPpreg and aP-aP-aPpreg), and the immune response in the mothers and their offspring, as well as the protection of the offspring against Bordetella pertussis challenge, were assessed. Pertussis toxin (PTx)-specific IgG responses were detected in mothers after both the second and third doses, with higher titers after the third dose, regardless of the vaccination schedule. However, a significant reduction in PTx-IgG levels was observed after 22 weeks post aPpreg immunization in mothers with the aP-aP-aPpreg scheme but not in the wP-wP-aPpreg immunized mothers. The aP-aP-aPpreg schedule triggered a murine antibody response mainly to a Th2-profile, while wP-wP-aPpreg induced a Th1/Th2 mixed profile. Both immunization schemes administered to the mothers protected the offspring against pertussis, but the wP-wP-aPpreg vaccination conferred offspring protection in all pregnancies at least up to 20 weeks after receiving the aPpreg-dose. In contrast, the immunity induced by aP-aP-aPpreg began to decline in births that occurred 18 weeks after receiving the aPpreg dose. For the aP-aP-aPpreg scheme, pups born from gestations furthest from aPpreg (+22 weeks) had lower PTx-specific IgG levels than those born closer to the application of the dose during pregnancy. In contrast, for pups born to wP-wP-aPpreg vaccinated mothers, the PTx-specific IgG levels were maintained over time, even for those born at the longest time studied (+22 weeks). It is noteworthy that only the pups born from mothers with aP-aP-aPpreg and receiving a neonatal dose of either aP or wP were more susceptible to B. pertussis infection than mice with only maternal immunity, suggesting interference with the induced immunity (p<0.05). However, it should be noted that mice with maternal immunity, whether vaccinated or not with neonatal doses, are better protected against colonization with B. pertussis than mice without maternal immunity but vaccinated with aP or wP.

Adverse infant outcomes following low-risk pregnancies in England: a retrospective cohort study

BACKGROUND

There are limited data describing adverse infant outcomes in infants born to women with a low risk of complications during pregnancy, such as those who may be enrolled in maternal immunization trials. This retrospective study estimated incidence proportions of infant outcomes in different cohorts of liveborn infants in England between 2005 and 2017.

METHODS

The incidence proportions of 10 infant outcomes were calculated for liveborn infants from pregnancies represented in the Clinical Practice Research Datalink (CPRD) Mother-Baby Link (MBL) and linkage to Hospital Episode Statistics (HES). Three infant cohorts were designed: (1) the all pregnancies infants cohort (N = 185,119), (2) the all pregnancies with a gestational age (GA) ≥ 24 weeks infants cohort (N = 183,869), and (3) the low-risk pregnancies infants cohort (LR infants cohort, N = 121,871), which included pregnancies with a GA ≥ 24 weeks and no diagnosis of predefined high-risk medical conditions until 24 weeks GA.

RESULTS

The most common adverse infant outcome in the three infant cohorts was macrosomia (e.g., 1,085.9/10,000 live births in the LR infants cohort), followed by minor congenital anomalies (e.g., 800.6/10,000 in the LR infants cohort), very low/low birth weight (e.g., 400.6/10,000 in the LR infants cohort), and major congenital anomalies (e.g., 270.4/10,000 in the LR infants cohort). The incidence proportions for early-onset sepsis, very low/low birth weight, and minor and major congenital anomalies were lower in the LR infants than in the other cohorts (non-overlapping confidence intervals [CIs]). The incidence proportions of neonatal death, infant death, late-onset sepsis, macrosomia, small for GA, and large for GA were similar between cohorts (overlapping CIs).

CONCLUSIONS

This study generated background rates of adverse infant outcomes from liveborn infants of all and low-risk pregnancies represented in the CPRD Pregnancy Register MBL and linkage to HES. The results indicate lower incidence proportions of several adverse infant outcomes in infants from low-risk pregnancies compared to all pregnancies, illustrating the importance of considering maternal risk factors. These background rates may facilitate the interpretation of safety data from maternal immunization trials and of pharmacovigilance data from maternal vaccines. They may also be of interest for other interventions studied in pregnant women.

Immunisation against COVID-19 in Pregnancy and of Women Planning Pregnancy

Following reports of the first human SARS-CoV2 infection in December 2019 from Wuhan Province, China, there was such rapid spread that by March 2021, the World Health Organization (WHO) had declared a pandemic. Over 6.5 million people have died from this infection worldwide, although this is most likely an underestimate. Until vaccines became available, mortality and severe morbidity were costly in terms of life lost as well as the cost of supporting the severely and acutely ill. Vaccination changed the landscape, and following worldwide adoption, life has gradually been returning to normal. The speed of production of the vaccines was unprecedented and undoubtedly ushered in a new era in the science of fighting infections. The developed vaccines were on the already known platforms for vaccine delivery: inactivated virus, virus vector, virus-like particles (VLP) subunit, DNA and mRNA. The mRNA platform was used for the first time to deliver vaccines to humans. An understanding of these platforms and the pros and cons of each are important for clinicians who are often challenged by the recipients on the advantages and risks of these vaccines. These vaccines have so far and reassuringly been shown to be safe in reproduction (with no effect on gametes) and pregnancy (not associated with congenital malformations). However, safety remains paramount and continuing vigilance is critical, especially against rare fatal complications such as vaccine-induced thrombocytopenia and myocarditis. Finally, the waning immunity months after vaccination means repeated immunisation is likely to be ongoing, but just how often and how many such revaccinations should be recommended remains uncertain. Research into other vaccines and alternate delivery methods should continue as this infection is likely to be around for a long time.

Unveiling the contributions of immunization for progressing towards Universal Health Coverage

The aim of the United Nations' Sustainable Development Goal (SDG)3 is to ensure healthy lives and promote well-being for all, at all ages; including reducing maternal and child mortality, combating communicable and non-communicable diseases, and achieving Universal Health Coverage (UHC). UHC aims to provide everyone with equal access to quality essential and comprehensive healthcare services including preventions, interventions, and treatments, without exposing them to financial hardship. Making progress toward UHC requires significant investment in technical and financial resources and countries are pursuing the implementation of cost-saving measures within health systems to help them achieve UHC. Whilst many countries are far from attaining UHC, all countries, particularly low- and middle-income countries, can take steps toward achieving UHC. This paper discusses key data showing how immunization is a fundamental, cost-effective tool for reducing morbidity and mortality associated with infectious disease in all populations, creating more productive communities, reducing treatment costs, and consequently, facilitating social and economic advancement. Immunization is key to advancing toward UHC by relieving the burden that diseases place on the healthcare services, freeing essential resources to use elsewhere within the healthcare system. Immunization is an essential, readily available strategy that countries can deploy to achieve UHC and the SDG3 agenda.

Protecting the Offspring, the Gift of Maternal Immunization: Current Status and Future Perspectives

Pregnancy is characterized by immunological alterations in pregnant women that permit the growth of a semi-allogenic fetus, resulting in greater susceptibility of childbearing women to infections. Furthermore, due to the immaturity of the immune system of neonates, a protection gap is present in early life, leaving neonates and infants vulnerable to infectious diseases with increased morbidity and mortality. Maternal immunization against influenza, pertussis, and, in the context of the COVID-19 pandemic, SARS-CoV-2 has been implemented in several countries, with beneficial effects on both the mother and the offspring. The main protective mechanism of vaccination during pregnancy is transplacental transfer of maternal antibodies. However, recent evidence has implied that the fetal immune system may be influenced beyond passive immunity. This review sheds light on the current status of the routinely administered vaccinations during pregnancy, focusing on the impact of maternal immunization on the priming of the fetal immune system and suggesting future perspectives for the optimization of vaccination strategies.

The adaptive immune system in early life: The shift makes it count

Respiratory infectious diseases encountered early in life may result in life-threatening disease in neonates, which is primarily explained by the relatively naive neonatal immune system. Whereas vaccines are not readily available for all infectious diseases, vaccinations have greatly reduced childhood mortality. However, repeated vaccinations are required to reach protective immunity in infants and not all vaccinations are effective at young age. Moreover, protective adaptive immunity elicited by vaccination wanes more rapidly at young age compared to adulthood. The infant adaptive immune system has previously been considered immature but this paradigm has changed during the past years. Recent evidence shows that the early life adaptive immune system is equipped with a strong innate-like effector function to eliminate acute pathogenic threats. These strong innate-like effector capacities are in turn kept in check by a tolerogenic counterpart of the adaptive system that may have evolved to maintain balance and to reduce collateral damage. In this review, we provide insight into these aspects of the early life's adaptive immune system by addressing recent literature. Moreover, we speculate that this shift from innate-like and tolerogenic adaptive immune features towards formation of immune memory may underlie different efficacy of infant vaccination in these different phases of immune development. Therefore, presence of innate-like and tolerogenic features of the adaptive immune system may be used as a biomarker to improve vaccination strategies against respiratory and other infections in early life.

Points to Consider in the Development and Information Provision of Vaccines for Vaccination during Pregnancy: A Survey

This report surveyed vaccination decisions during pregnancy based on the package inserts of vaccines approved in Japan, the USA, and Europe. Furthermore, it evaluates vaccination decision-making factors based on the characteristics of the target infections and the modality of the vaccines. Live vaccines known to cause fetal abnormalities are contraindicated for pregnant women, whereas vaccines for life-threatening infectious diseases are authorized for administration during pregnancy when the need is recognized, even for live vaccines. We compared the World Health Organization and European Medicines Agency guidelines on the development of vaccines for pregnant women and surveyed the details of the studies to collect information on SARS-CoV-2 vaccination during pregnancy. In compliance with the guidelines, for all SARS-CoV-2 vaccines, non-clinical reproductive and developmental toxicity studies and clinical trials including non-pregnant women of childbearing age were conducted prior to the vaccination of pregnant women. For all vaccines, information from registries on vaccination during pregnancy are used for post-marketing surveillance. While it is desirable to vaccinate women before pregnancy through planned immunization, whenever possible, pandemics such as H1N1 influenza and COVID-19 may require vaccination even during pregnancy. Necessary and sufficient studies for the decision of vaccination during pregnancy should be carried out promptly.

Operational lessons learned in conducting an international study on pharmacovigilance in pregnancy in resource-constrained settings: The WHO Global Vaccine safety Multi-Country collaboration project

The WHO Global Vaccine Safety Multi-Country Collaboration study on safety in pregnancy aims to estimate the minimum detectable risk for selected perinatal and neonatal outcomes and assess the applicability of standardized case definitions for study outcomes and maternal immunization in low- and middle-income countries (LMICs). This paper documents the operational lessons learned from the study. A prospective observational study was conducted across 21 hospitals in seven countries. All births occurring at sites were screened to identify select perinatal and neonatal outcomes from May 2019 to August 2020. Up to 100 cases per outcome were recruited to assess the applicability of standardized case definitions. A multi-pronged study quality assurance plan was implemented. The impact of the COVID-19 pandemic on site functioning and project implementation was also assessed. Multi-layered ethics and administrative approvals, limited clinical documentation, difficulty in identifying outcomes requiring in-hospital follow-up, and poor quality internet connectivity emerged as important barriers to study implementation. Use of electronic platforms, application of a rigorous quality assurance plan with frequent interaction between the central and site teams helped improve data quality. The COVID-19 pandemic disrupted data collection for up to 6 weeks in some sites. Our study succeeded in establishing an international hospital-based surveillance network for evaluating perinatal and neonatal outcomes using common study protocol and procedures in geographically diverse sites with differing levels of infrastructure, clinical and health-utilization practices. The enhanced surveillance capacity of participating sites shall help support future pharmacovigilance efforts for pregnancy interventions.

Safety and protective capability of an inactivated SARS-CoV-2 vaccine on pregnancy, lactation and the growth of offspring in hACE2 mice

The mass inoculation of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine to induce herd immunity is one of the most effective measures to fight COVID-19. The vaccination of pregnant women cannot only avoid or reduce the probability of infectious diseases, but also offers the most effective and direct protection for neonates by means of passive immunization. However, there is no randomized clinical data to ascertain whether the inactivated vaccination of pregnant women or women of childbearing age can affect conception and the fetus. We found that human angiotensin-converting enzyme 2 (hACE2) mice that were vaccinated with two doses of CoronaVac (an inactivated SARS-CoV-2 vaccine) before and during pregnancy exhibited normal weight changes and reproductive performance indices; the physical development of their offspring was also normal. Following intranasal inoculation with SARS-CoV-2, pregnant mice in the immunization group all survived; reproductive performance indices and the physical development of offspring were all normal. In contrast, mice in the non-immunization group all died before delivery. Analyses showed that inoculation of CoronaVac was safe and did not exert any significant effects on pregnancy, lactation, or the growth of offspring in hACE2 mice. Vaccination effectively protected the pregnant mice against SARS-CoV-2 infection and had no adverse effects on the growth and development of the offspring, thus suggesting that inoculation with an inactivated SARS-CoV-2 vaccine may be an effective strategy to prevent infection in pregnant women.

Case Report: Post-Partum SARS-CoV-2 Infection After the First French Uterus Transplantation

Absolute uterus factor infertility, whether congenital or acquired, renders the woman unable to carry a child. Although uterus transplantation (UTx) is being increasingly performed as a non-vital procedure to address this unfortunate condition, the immunosuppression required presents risks that are further compounded by pregnancy and during the puerperium period. These vulnerabilities require avoidance of SARS-CoV-2 infection in pregnant UTx recipients especially during the third trimester, as accumulating evidence reveals increased risks of morbidity and mortality. Here we describe a successful UTx case with delivery of a healthy child, but in which both mother and neonate developed asymptomatic SARS-CoV-2 infection seven days after RNA vaccination, on day 35 post-partum. Although the patient was successfully treated with a combination therapy comprised of two monoclonal antibodies, this case highlights the challenges associated with performing UTx in the era of Covid-19. More broadly, the risks of performing non-vital organ transplantation during a pandemic should be discussed among team members and prospective patients, weighing the risks against the benefits in improving the quality of life, which were considerable for our patient who achieved motherhood with the birth of a healthy child.

Knowledge, Perceptions, Attitudes and Practices of Midwives Regarding Maternal Influenza and Pertussis Vaccination: A Qualitative Study

The coverage of maternal vaccination against pertussis and, particularly, influenza is lower than expected. The lack of recommendation from healthcare providers conditions non-vaccination in pregnant women. The purpose was to determine the knowledge, perceptions, attitudes and practices of midwives regarding maternal influenza and pertussis vaccination. A qualitative descriptive study based on semi-structured, face-to-face interviews with seventeen midwives was conducted, including purposive sampling and thematic analyses. Midwives had disparate knowledge and perceptions about the severity of influenza and pertussis in pregnant women, and influenza was not considered very serious. The vaccines were generally considered safe. However, because midwives did not have enough information about the safety of the influenza vaccine, there was a tendency not to recommend it. While most midwives had a positive attitude toward vaccination, their advocation for vaccination against influenza was not as clear as it was for pertussis. Not wanting to influence the decision and assuming an informative–facilitating role also led providers to recommend the influenza vaccine less frequently. Midwives are among the main sources of professional advice for pregnant women. Addressing their understanding and professional practices regarding maternal vaccination is key to change the attitude of pregnant women and thus increase vaccine uptake among them, particularly for influenza.

Three Dose Levels of a Maternal Respiratory Syncytial Virus Vaccine Candidate Are Well Tolerated and Immunogenic in a Randomized Trial in Nonpregnant Women

BACKGROUND

Respiratory syncytial virus (RSV) causes respiratory tract infections, which may require hospitalization especially in early infancy. Transplacental transfer of RSV antibodies could confer protection to infants in their first months of life.

METHODS

In this first-in-human, placebo-controlled study, 502 healthy nonpregnant women were randomized 1:1:1:1 to receive a single dose of unadjuvanted vaccine containing 30/60/120 µg of RSV fusion (F) protein stabilized in the prefusion conformation (RSVPreF3) or placebo.

RESULTS

Solicited local adverse events (AEs) were more frequently reported in the RSVPreF3 groups (4%-53.2%) versus placebo (0%-15.9%); most were mild/moderate. Unsolicited AEs were comparably reported among groups. Three serious AEs were reported; none was vaccination-related. Compared with prevaccination values, anti-RSV A neutralizing antibody geometric mean titers and anti-RSVPreF3 immunoglobulin G geometric mean concentrations increased 8- to 14-fold and 12- to 21-fold at day 8 and persisted 5- to 6-fold and 6- to 8-fold higher until day 91 in the RSVPreF3 groups versus 1-fold in placebo. Comparisons at day 8 and day 31 showed that the higher dose levels were significantly more immunogenic than the lowest one.

CONCLUSIONS

The RSVPreF3 vaccine was well tolerated and immunogenic. The 60 and 120 µg dose levels were selected for further investigation in pregnant women.

CLINICAL TRIALS REGISTRATION

NCT03674177.

Facilitating safety evaluation in maternal immunization trials: a retrospective cohort study to assess pregnancy outcomes and events of interest in low-risk pregnancies in England

BACKGROUND

Maternal characteristics like medical history and health-related risk factors can influence the incidence of pregnancy outcomes and pregnancy-related events of interest (EIs). Data on the incidence of these endpoints in low-risk pregnant women are needed for appropriate external safety comparisons in maternal immunization trials. To address this need, this study estimated the incidence proportions of pregnancy outcomes and pregnancy-related EIs in different pregnancy cohorts (including low-risk pregnancies) in England, contained in the Clinical Practice Research Datalink (CPRD) Pregnancy Register linked to Hospital Episode Statistics (HES) between 2005 and 2017.

METHODS

The incidence proportions of 7 pregnancy outcomes and 15 EIs were calculated for: (1) all pregnancies (AP) represented in the CPRD Pregnancy Register linked to HES (AP cohort; N = 298 155), (2) all pregnancies with a gestational age (GA) ≥ 24 weeks (AP24+ cohort; N = 208 328), and (3) low-risk pregnancies (LR cohort; N = 137 932) with a GA ≥ 24 weeks and no diagnosis of predefined high-risk medical conditions until 24 weeks GA.

RESULTS

Miscarriage was the most common adverse pregnancy outcome in the AP cohort (1 379.5 per 10 000 pregnancies) but could not be assessed in the other cohorts because these only included pregnancies with a GA ≥ 24 weeks, and miscarriages with GA ≥ 24 weeks were reclassified as stillbirths. Preterm delivery (< 37 weeks GA) was the most common adverse pregnancy outcome in the AP24+ and LR cohorts (742.9 and 680.0 per 10 000 pregnancies, respectively). Focusing on the cohorts with a GA ≥ 24 weeks, the most common pregnancy-related EIs in the AP24+ and LR cohorts were fetal/perinatal distress or asphyxia (1 824.3 and 1 833.0 per 10 000 pregnancies), vaginal/intrauterine hemorrhage (799.2 and 729.0 per 10 000 pregnancies), and labor protraction/arrest disorders (752.4 and 774.5 per 10 000 pregnancies).

CONCLUSIONS

This study generated incidence proportions of pregnancy outcomes and pregnancy-related EIs from the CPRD for different pregnancy cohorts, including low-risk pregnancies. The reported incidence proportions of pregnancy outcomes and pregnancy-related EIs are largely consistent with external estimates. These results may facilitate the interpretation of safety data from maternal immunization trials and the safety monitoring of maternal vaccines. They may also be of interest for any intervention studied in populations of pregnant women.

Determinants of neonatal sepsis among neonates admitted to the neonatal intensive care unit of public hospitals in Hawassa City Administration, Sidama Region, Ethiopia, 2020: an unmatched, case-control study

OBJECTIVE

This study was conducted to assess the determinants of neonatal sepsis in the neonatal intensive care units of public hospitals in Hawassa City Administration, Sidama Region, Ethiopia, in 2020.

DESIGN

Institutional-based, unmatched, case-control study.

SETTING

The study was conducted in three public hospitals (Hawassa University Teaching Hospital, Adare General Hospital and Hawela Tula Primary Hospital) of Hawassa City, Ethiopia.

PARTICIPANTS

A total of 331 (110 cases and 221 controls) neonates with their index mothers were included in the study from 1 August to 30 September 2020.

OUTCOME MEASURES

A pretested, interviewer-administered questionnaire and data extraction checklist were used to collect data. Data were coded and entered into EpiData V.3.1 before being exported to SPSS V.20 for analysis. The factors associated with neonatal sepsis were assessed using bivariable and multivariable logistic regression analyses. P value of less than 0.05 was used to establish statistically significant association of variables.

RESULTS

Caesarean section delivery (adjusted OR (AOR)=2.56, 95 % CI 1.3 to 5.00), maternal anaemia (AOR=2.58, 95 % CI 1.45 to 4.6) and lack of vaccination with tetanus toxoid (AOR=3.5, 95% CI 2.07 to 6.19) were all identified as factors significantly associated with neonatal sepsis.

CONCLUSIONS

Caesarean section delivery, maternal history of anaemia and lack of vaccination with tetanus toxoid were found to be risk factors for neonatal sepsis. Establishing preconception care practice, strengthening the quality of antenatal care and standardising infection prevention practice are needed to improve neonatal health.

Functional and structural modifications of influenza antibodies during pregnancy

Pregnancy represents a unique tolerogenic immune state which may alter susceptibility to infection and vaccine response. Here, we characterized humoral immunity to seasonal influenza vaccine strains in pregnant and non-pregnant women. Although serological responses to influenza remained largely intact during late pregnancy, distinct modifications were observed. Pregnant women had reduced hemagglutinin subtype-1 (H1)- IgG, IgG1, IgG2, and IgG3, hemagglutination inhibition, and group 1 and 2 stem IgG titers. Intriguingly, H1-specific avidity and FcγR1 binding increased, and influenza antibodies had distinct Fc and Fab glycans characterized by increased di-galactosylation and di-sialylation. H1-specific Fc-functionality (i.e. monocyte phagocytosis and complement deposition) was moderately reduced in pregnancy. Multivariate antibody analysis revealed two distinct populations (pregnant vs. non-pregnant) segregated by H1 FcγR1 binding, H1-IgG levels, and Fab and Fc glycosylation. Our results demonstrated a structural and functional modulation of influenza humoral immunity during pregnancy that was antigen-specific and consistent with reduced inflammation and efficient placental transport.

Experts' Opinion for Improving Pertussis Vaccination Rates in Adolescents and Adults: A Call to Action

This article highlights the importance of diphtheria-tetanus-acellular pertussis (with reduced antigen content, dTap) vaccination in preventing pertussis, a respiratory infection that is still widespread and easily transmitted. In particular, it highlights the need to receive a booster vaccination throughout life to maintain high antibody levels, which decrease through time. This document collects the opinions that emerged from the comparison between major Italian experts in the field of vaccination. This working group was created to promote a "call to action", aimed at raising awareness among all institutions, public health authorities, and health workers involved in the vaccination process, about the importance of dTap vaccine administration and with the mindset of implementing the strategic vaccination plan provided by the National Vaccine Plan (NVP). In fact, despite this vaccine being included in the NVP, there are some issues attributable to the practice of vaccination (local health authorities, vaccination centers, occupational health services, gynecology centers, societies of work). Therefore, it is necessary that the Ministry defines the vaccination coverage objectives, identifies the groups of subjects who should receive the booster vaccine (subjects exposed to greater risk of infection, subjects over 60, pregnant women), and applies all the necessary measures to encourage the implementation of this practice.

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

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

Attitude for vaccination prophylaxis among pregnant women: a cross-sectional study

Pregnant women and newborns are considered a subgroup of population at increased risk for several infectious diseases, some of which are vaccine-preventable. Anti-diphtheria-tetanus-pertussis vaccine (dTpa) and influenza vaccine are recommended for pregnant women. We carried out a study to evaluate the knowledge of new mothers toward the main vaccine-preventable diseases and to assess their compliance with recommended vaccinations. Using the Hospital Discharge Forms (SDO), the list of women who gave birth in 2018 was generated. Women were interviewed by a questionnaire administered by telephone. The study sample consisted of 145 subjects, with an average age of 35.0 ± 5.9 years (range = 18.0–47.0). 5/145 (3.4%; 95% CI = 1.1–7.9%) subjects were advised during pregnancy to have the flu shot; only 1/145 (0.7%; 95% CI = 0.5–71.6%) reported the flu vaccine during the last pregnancy. 94/145 (64.8%; 95% CI = 57.2–73.2%) respondents declared that they had carried out the TORCH panel exams before pregnancy; of these 18/94 (19.2%; 95% C = 11.8–28.6%) were susceptible for rubella. Of these subjects, for 7/18 (38.9%; 95% CI = 17.3–64.3%) rubella vaccination was offered and 5/7 (71.4%; 95% CI = 29.0–96.3%) decided to carry out the vaccination. Only 1/145 (0.7%; 95% CI = 0.0–3.8%) of the interviewed woman underwent anti-dTap vaccination. Greater efforts must be made by public health institutions to raise awareness and improve vaccination compliance in this population.

An Update on the Status of Vaccine Development for SARS-CoV-2 Including Variants. Practical Considerations for COVID-19 Special Populations

The progress in the development of various vaccine platforms against SARS-CoV-2 have been rather remarkable owing to advancement in molecular and biologic sciences. Most of the current vaccines and those in development focus on targeting the viral spike proteins by generating antibodies of varying spectrum. These vaccines represent a variety of platforms including whole virus vaccines, viral vector vaccines, nucleic acid vaccines representing RNA, DNA, and their hybrid forms.The therapeutic efficacy of these vaccines varies owing to their pharmacodynamic individualities. COVID-19 variants are capable of inducing different pathologic responses and some of which may be resistant to antibodies generated by current vaccines. The current clinical use of these vaccines has been through emergency use authorization until recently. Moreover, the efficacy and safety of these vaccines have been tested in substantial numbers of individuals but studies in special populations that better reflect the global population are pending results. These specialized populations include young children, immunocompromised patients, pregnant individuals, and other specialized groups. Combination approaches, molecularly modified vaccination approaches, and vaccines conferring longer periods of immunity are being currently being investigated, as well as pharmacovigilance studies.The continual transformation of SARS-CoV-2 and its variants are of concern along with the breakthrough infections. These considerations pose new challenges for the development of vaccination platforms. For this purpose, booster doses, combination vaccine approaches, and other modalities are being discussed. This review provides an updated account of currently available vaccines and those in advanced development with reference to their composition and mechanisms of action.A discussion on the use of vaccines in special populations including immunocompromised patients, pregnant women and other specialized populations are also included.

Dyspnea and COVID-19: A Review of Confounding Diagnoses during the Postpartum Period

The puerperium is a complex period that begins with placental delivery and lasts for 6 weeks, during which readaptation of the female organism and redistribution of blood volume occur. This period is conducive to the occurrence of thromboembolic events. In the context of the SARS-CoV-2 pandemic, the virus responsible for COVID-19, the attention of the scientific community and health professionals has been focused on obtaining insights on different aspects of this disease, including etiology, transmission, diagnosis, and treatment. Regarding the pregnancy-postpartum cycle, it is opportune to review the clinical conditions that can occur during this period and to investigate dyspnea as a postpartum symptom in order to avoid its immediate association with COVID-19 without further investigation, which can lead to overlooking the diagnosis of other important and occasionally fatal conditions.

Improving uptake of vaccines in pregnancy: A service evaluation of an antenatal vaccination clinic at a tertiary hospital in the UK

Background

Vaccination against pertussis and seasonal influenza is recommended for all pregnant women in the UK. More recently COVID-19 vaccination has also been offered to women in pregnancy.

Objectives

To evaluate the uptake of vaccines in pregnant women within a midwife-led immunisation clinic and to assess factors influencing pregnant women's decisions about accepting vaccination.

Methods

Uptake of vaccines amongst pregnant women referred to a single UK centre for antenatal care between 01/01/19 and 02/10/19 was assessed. Interviews with 20 pregnant women explored views of antenatal vaccination and experiences of the vaccination service.

Findings

Amongst 4420 women, uptake was 90.6% for pertussis and 78.8% for influenza vaccines. Factors influencing vaccine-related decision-making amongst 20 interviewed women were: healthcare professional recommendation, perceived susceptibility and risk of infection, and previous experience of vaccination and vaccine-preventable disease.

Conclusions and Implications for Practice

Uptake of pertussis and influenza vaccines within a secondary care immunisation service was higher than the national or regional average. The model of vaccine delivery was associated with high levels of satisfaction. This model of vaccine delivery could be implemented elsewhere to increase vaccine uptake, and should be considered for delivery of COVID-19 vaccines in the future.

Vaccination in pregnancy against pertussis and seasonal influenza: key learnings and components from high-performing vaccine programmes in three countries: the United Kingdom, the United States and Spain

BACKGROUND

Pertussis and seasonal influenza are responsible for significant maternal, neonatal, and infant morbidity and mortality, but vaccine coverage rates (VCR) for both pertussis (administered as a tetanus, diphtheria, acellular pertussis [Tdap] vaccination) and seasonal influenza in pregnancy remain generally low. Only a small number of countries, including Spain, the United Kingdom (UK), and the United States (US), have high Tdap and seasonal influenza VCRs in pregnancy. The purpose of this study was to identify the key factors that contributed to the high VCRs observed in these countries.

METHODS

The experience from both Tdap and seasonal influenza vaccination programmes during pregnancy were documented in Spain, the UK, and the US using a three-step approach. A literature review yielded 157 publications, and a further 117 documents were selected through desk research. A published five-pillar VCR framework for influenza was amended to evaluate the specific contributing factors leading to high Tdap and seasonal influenza VCRs among pregnant women.

RESULTS

The analysis identified components that contributed to higher VCR in pregnant women across three different healthcare systems in Spain, UK, and US. The combination of several key interventions in each country led to a rapid increase in VCR that reached near-optimal levels (i.e. 75% for seasonal influenza) within a few years. As well as inclusion in national immunisation programme and vaccine reimbursement, key components that were identified included the mobilisation of health authorities, prenatal care Healthcare Professionals (HCP) and scientific societies, the inclusion of vaccination in antenatal medical guidance, the provision of educational material to HCPs, and a strong disease awareness driven by recent pertussis outbreaks in each country.

CONCLUSIONS

Although there is no simple, universal solution to improving sub-optimal VCRs, the list of components identified in this study from three countries with high-performing Tdap and seasonal influenza vaccination programmes provides a basis for public health and medical stakeholders in other countries to define strategies to successfully implement national vaccination programmes for pregnant women.

Pooled Prevalence of Adverse Pregnancy and Neonatal Outcomes in Malawi, South Africa, Uganda, and Zimbabwe: Results From a Systematic Review and Meta-Analyses to Inform Trials of Novel HIV Prevention Interventions During Pregnancy

Background: Robust data summarizing the prevalence of pregnancy and neonatal outcomes in low- and middle-income countries are critically important for studies evaluating investigational products for HIV prevention and treatment in pregnant and breastfeeding women. In preparation for studies evaluating the safety of the dapivirine vaginal ring for HIV prevention in pregnancy, we conducted a systematic literature review and meta-analyses to summarize the prevalence of pregnancy and neonatal outcomes in Malawi, South Africa, Uganda, and Zimbabwe.

Methods: Ten individual systematic literature reviews were conducted to identify manuscripts presenting prevalence data for 12 pregnancy and neonatal outcomes [pregnancy loss, stillbirth, preterm birth, low birthweight (LBW), neonatal mortality, congenital anomaly, chorioamnionitis, postpartum endometritis, postpartum hemorrhage, gestational hypertension, preeclampsia/eclampsia, and preterm premature rupture of membranes (PPROM)]. Studies included in the meta-analyses were published between January 1, 1998, and July 11, 2018, provided numerator and denominator data to support prevalence estimation, and included women of any HIV serostatus. Random-effects meta-analyses were conducted to estimate the pooled prevalence and 95% confidence interval (CI) for each outcome overall, by country, and by HIV status.

Results: A total of 152 manuscripts were included across the 12 outcomes. Overall, the frequency of stillbirth (n = 75 estimates), LBW (n = 68), and preterm birth (n = 67) were the most often reported. However, fewer than 10 total manuscripts reported prevalence estimates for chorioamnionitis, endometritis, or PPROM. The outcomes with the highest pooled prevalence were preterm birth (12.7%, 95%CI 11.2–14.3), LBW (11.7%, 95%CI 10.6–12.9), and gestational hypertension (11.4%, 95%CI 7.8–15.7). Among the outcomes with the lowest pooled prevalence estimates were neonatal mortality (1.7%, 95%CI 1.4–2.1), pregnancy loss [1.9%, 95%CI 1.1–2.8, predominately studies (23/29) assessing losses occurring after the first trimester], PPROM (2.2%, 95%CI 1.5–3.2), and stillbirth (2.5%, 95%CI 2.2–2.7).

Conclusions: Although this review identified numerous prevalence estimates for some outcomes, data were lacking for other important pregnancy-related conditions. Additional research in pregnant populations is needed for a thorough evaluation of investigational products, including for HIV prevention and treatment, and to inform better estimates of the burden of adverse pregnancy outcomes globally.

Transplacental Antibody Transfer of Respiratory Syncytial Virus Specific IgG in Non-Human Primate Mother-Infant Pairs

One approach to protect new-borns against respiratory syncytial virus (RSV) is to vaccinate pregnant women in the last trimester of pregnancy. The boosting of circulating antibodies which can be transferred to the foetus would offer immune protection against the virus and ultimately the disease. Since non-human primates (NHPs) have similar reproductive anatomy, physiology, and antibody architecture and kinetics to humans, we utilized this preclinical species to evaluate maternal immunization (MI) using an RSV F subunit vaccine. Three species of NHPs known for their ability to be infected with human RSV in experimental challenge studies were tested for RSV-specific antibodies. African green monkeys had the highest overall antibody levels of the old-world monkeys evaluated and they gave birth to offspring with anti-RSV titers that were proportional to their mother. These higher overall antibody levels are associated with greater durability found in their offspring. Immunization of RSV seropositive AGMs during late pregnancy boosts RSV titers, which consequentially results in significantly higher titers in the vaccinated new-borns compared to the new-borns of unvaccinated mothers. These findings, accomplished in small treatment group sizes, demonstrate a model that provides an efficient, resource sparing and translatable preclinical in vivo system for evaluating vaccine candidates for maternal immunization.

[Vaccination during pregnancy]

Hintergrund

Schwangere, Feten und Säuglinge weisen aufgrund von Besonderheiten ihres Immunsystems eine erhöhte infektionsbedingte Morbidität und Mortalität auf, die durch den Einsatz von Impfungen während der Schwangerschaft reduziert werden kann.

Ziel

In diesem Beitrag werden die Wirkungsweise, die Evidenz der zu erwartenden Effekte, Kontraindikationen und mögliche Nebenwirkungen von Impfungen in der Schwangerschaft erläutert.

Methode

Es wurde eine selektive Literaturrecherche unter besonderer Berücksichtigung der Empfehlungen der Ständigen Impfkommission am Robert Koch-Institut (STIKO) und einschlägiger Leitlinien durchgeführt.

Ergebnisse

Impfungen in der Schwangerschaft schützen die werdende Mutter vor schweren Verläufen einzelner Infektionskrankheiten und damit verbundenen Schwangerschaftskomplikationen. Zudem vermitteln sie dem Neugeborenen durch die vertikale Übertragung mütterlicher Antikörper einen passiven Immunschutz vor lebensbedrohlichen Infektionen. Für die Impfung mit inaktivierten Impfstoffen gegen Tetanus, Influenza und Pertussis sind Wirksamkeit und Sicherheit gut belegt. Impfungen mit Lebendvakzinen sind wegen ihres theoretischen Risikos für den Fetus kontraindiziert. Die Datenlage zur Anwendung der Impfstoffe gegen die „coronavirus disease 2019“ (COVID 19) ist noch limitiert.

Diskussion

Impfungen in der Schwangerschaft zielen auf den direkten Schutz der Schwangeren durch aktive Immunisierung und/oder des Kindes durch natürliche passive Immunisierung. Schwangere sollten von einer indizierten Impfung zum eigenen Schutz und dem des Kindes nicht ausgeschlossen werden. Zusätzliche sinnvolle Maßnahmen zum Schutz der Gesundheit von Mutter und Kind sind die Impfung enger Kontaktpersonen sowie das Schließen relevanter Impflücken junger Erwachsener, insbesondere bei Frauen im gebärfähigen Alter.

Maternal immunization: trends in South and Southeast Asian countries

Maternal immunization has the potential to reduce neonatal deaths caused by vaccine-preventable infectious diseases. Elimination of maternal and neonatal tetanus from many countries illustrates the potential benefits of maternal immunization as a strategy to decrease neonatal mortality caused by vaccine-preventable infections. Many countries in South and Southeast Asia have high cases of neonatal deaths, which were historically attributed to vaccine-preventable infections. Still, these countries vary in recommendations regarding immunization of pregnant women. We reviewed the current recommendations for the use of tetanus toxoid, tetanus-diphtheria, or tetanus-diphtheria-acellular pertussis (Tdap) vaccines for immunization of pregnant women. In addition to protection against tetanus and diphtheria, administration of the Tdap vaccine to pregnant women could help protect neonates against pertussis until they can receive the first two vaccine doses of their primary course. Vaccination against seasonal influenza is also recommended in many countries worldwide for pregnant women as influenza can pose health risks for the mother-fetus unit and the infant. Despite the recognized benefit of influenza vaccination for pregnant women, only some South and Southeast Asian countries have implemented its recommendation. The success of maternal tetanus vaccination has kindled the interest in vaccines that can be safely administered during pregnancy. Future availability of vaccines against respiratory syncytial virus and group B streptococcus, for use in pregnant women, could help prevent neonatal infections, especially in regions where diseases are less controlled. Communicating the body of evidence that supports maternal immunization to obstetricians is key for achieving optimal vaccination coverage to ensure protection of neonates. The current review aims to create awareness about the existing and potential benefits of maternal immunization in South and Southeast Asia.

Acceptance of Pertussis Vaccination among Pregnant Women in Taiwan

This cross-sectional study assessed prenatal pertussis vaccination acceptance in Taiwan. A sample of pregnant women from five private clinics in Taiwan was recruited. Demographics, experience of prenatal vaccinations, key considerations, knowledge, and attitude about pertussis and its vaccination were measured. Among 505 participants, the vaccination rate, including planned vaccination, was 29.7%. Factors associated with acceptance included clinic location, primary caregiver of the newborn, newborns with siblings, previous influenza vaccination history, knowledge and attitude toward pertussis and its vaccination. Public health agencies should provide free vaccinations, clarify misinformation, and publicize prevention information, to improve prenatal pertussis vaccination acceptance.

A M2 protein-based universal influenza vaccine containing Advax-SM adjuvant provides newborn protection via maternal or neonatal immunization

BACKGROUND

Despite newborns being at increased risk of serious influenza infection, influenza vaccines are currently not recommended for use in infants under 6 months of age. We therefore sought to evaluate the protective efficacy in mice of an M2-based influenza vaccine (CapM2e) formulated with Advax-SM adjuvant. Vaccine protection was assessed via both passive maternal immunization and direct neonatal immunization.

METHODS

For maternal transfer studies, female mice were immunized 1 week before and after mating. Blood was collected from both mother and offspring during weaning and pups were challenged when they reached 3 weeks of age with lethal doses of H1N1 and homologous reassortment influenza strain H3N2 with conserved M2. For direct immunization studies, newborns were immunized at 1 and 3 weeks of age and blood was collected prior to challenge at 4 weeks of age.

RESULTS

Maternal immunization with CapM2e + Advax-SM vaccine induced high maternal M2e antibody levels that were passively transferred to their offspring and provided them with protection against both H1N1 and H3N2 influenza strains when challenged at 3 weeks of age. When used for direct immunization of neonatal mice, CapM2e + Advax-SM vaccine similarly induced high serum M2e antibody levels and protected against H1N1 and H3N2 influenza challenges with protection associated with inhibition of virus replication with a significant reduction in lung virus load in immunized pups.

CONCLUSION

CapM2e + Advax-SM vaccine could be useful for protecting newborns against diverse influenza A strains, with opportunities to achieve protection by passive maternal immunization or active neonatal immunization. This data supports further development of this promising M2e-based vaccine candidate.

Protective vaccinations during pregnancy - adult Poles knowledge in this area

BACKGROUND

The vaccine is a preparation of biological origin containing antigens that stimulate the body's immune system to produce acquired immunity. Vaccines can contain killed or "live" (attenuated) microorganisms as well as fragments of these (antigens). Although many vaccines are used routinely in pregnancy to provide a seroprotective immune response for mother, fetus and neonate there is much controversy over their use during this unique time. The aim of the study was to find out about the knowledge of adult Poles on the use of preventive vaccinations during pregnancy.

METHODS

The study involved 700 people (100%) aged 18 to 80 years ([Formula: see text] = 32.16 ± 16.46). Most of the respondents were women (511; 73%). The study consisted of 9 questions about preventive vaccinations of pregnant women and 5 questions about members of the studied group. The aforementioned questions formed the basis of the preparation of the presented article.

RESULTS

A significant part of respondents (322; 46%) did not have knowledge on the topic of safeness of using preventive vaccinations during pregnancy, 196 (28%) respondents believed that such procedure is not safe. Most of the respondents (371; 53%) did not know about the possibility of using "live" vaccines during pregnancy. 14 (2%) of respondents believed that pregnancy should be terminated in case of administration of a "live" vaccine to a pregnant woman. According to 294 (42%) respondents, vaccinations with "live" vaccines should be completed at least 3 months before the planned pregnancy. The subjects were not aware of the issue of post-exposure vaccination against tetanus and rabies among pregnant women. The respondents' responses were divided on the issue of the safest trimester of pregnancy for vaccine administration. Almost 1/3 of the respondents (203; 29%) indicated the third trimester as the safest for their performance.

CONCLUSION

The knowledge of the surveyed group, the majority of whom were women, about the use of vaccinations before and during pregnancy was unsatisfactory. There is a need to educate the public about the benefits and risks of performing or avoiding preventive vaccinations during pregnancy.

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.

The intent of students to vaccinate is influenced by cultural factors, peer network, and knowledge about vaccines

Young adults are the future vaccine decision-makers as parents or health-care professionals. To understand their attitudes and behaviors toward vaccination, we conducted a cross-sectional survey of 2079 students attending the University of Antwerp, Belgium and the University of Pisa, Italy. Principal component analysis was used to investigate associations between survey responses and the intent to vaccinate. Vaccination knowledge, attitudes, and behaviors among university students in Italy and Belgium were high. However, only one-half of respondents displayed an intent to vaccinate. High levels of knowledge, positive attitudes, and confidence in vaccines were positively associated with age, higher level of study, being a medical student, a recent vaccination experience, and not knowing trusted persons who did not believe in vaccines. Country of origin was highly correlated with the survey responses and was clustered with lifestyle, family, and data source variables, suggesting a strong modifying effect of culture and family attitudes on how vaccines are perceived in this age-group. Recent meningococcal vaccination campaigns and public discussions around mandatory vaccination in Italy may have influenced these results. We show that the intent to vaccinate was correlated with two main clusters of variables linked to culture (country, family, lifestyle), and to scholarship (knowledge, attitudes, data source) that together influence the behavior of students with respect to vaccination. Our study reinforces previous findings that knowledge about vaccines is key to shaping attitudes and behaviors, but also shows that cultural and lifestyle factors are another platform that could be leveraged in promoting vaccination among young people.

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.

Methodologic approaches in studies using real-world data to measure pediatric safety and effectiveness of vaccines administered to pregnant women: a scoping review protocol

OBJECTIVE

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

INTRODUCTION

In the United States, 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). Because of the ethical constraints in conducting randomized clinical trials to measure the effects on the infant, there is great interest in using electronic health care data or administrative claims data to study the effects of maternal immunization on the infant's health, and it is anticipated that such studies may be submitted to support regulatory decision-making. This scoping review will map the studies conducted to date that address these questions and provide a context for considering the regulatory issues that may arise in the future.

INCLUSION CRITERIA

Studies that report on pregnant women receiving immunization and the effectiveness or safety outcomes in their infants will be included. Study participants may be from any population or country, of any reproductive age, and with any health status. Studies will be included if they use real-world data (from electronic health records, administrative claims, pharmacy benefit records, or registries).

METHODS

An electronic search of PubMed and Embase will identify citations for screening. The search will be limited to studies published in English during the preceding 10 years. Two reviewers will screen citations in a two-step process (titles and abstracts, then full-text articles), and two reviewers will extract data for summary and synthesis.

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

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

Vaccination in Pregnancy

BACKGROUND

Vaccination during pregnancy can protect both the expecting mother and the unborn and newborn child from infectious diseases.

METHODS

This review is based on publications retrieved by a selective literature search on the immunological particularities of infectious diseases affecting pregnant women, unborn children, and neonates, with particular attention to the guidelines of the German Standing Committee on Vaccinations (Ständige Impfkommission, STIKO) and the pertinent guidelines.

RESULTS

Vaccination during pregnancy protects the expecting mother from a severe course of a number of different infectious diseases. Vaccination with inactivated vaccines against influenza, tetanus, and pertussis is effective, safe, and well tolerated. Women who are pregnant or of child-bearing age should be immunized against tetanus according to the STIKO recommendations. All pregnant women from the second trimester onward should receive an inactivated quadrivalent influenza vaccine. The immunity acquired after vaccination with an acellular pertussis vaccine is present only for a limited time. In a cohort study involving 72,781 pregnant women, pertussis vaccination during pregnancy was found to yield 91% protection against pertussis for their subsequently born children in the first three months of life. Further types of vaccine can also be given during pregnancy if indicated. Additional reasonable measures to protect the health of mother and child include the vaccination of other persons in close contact as well as the closure of relevant vaccination gaps among young adults, particularly women of child-bearing age. Treating physicians play a crucial role in encouraging vaccine acceptance by their patients.

CONCLUSION

Maternal immunization is a safe and effective strategy for giving neo - nates passive immune protection against life-threatening infections by the vertical transmission of maternal antibodies until they are able to build up their own adaptive immunity.

Healthcare providers' interpretations of product labelling information developed through a consensus stakeholder approach

BACKGROUND

The World Health Organization recommends immunization with inactivated influenza vaccine (IIV) and tetanus-diphtheria-acellular pertussis (Tdap) vaccine during pregnancy. Yet, product labelling information for IIV and Tdap sends a different message. In a previous study, we developed evidence-based statements about vaccination in pregnancy that could be included in product information. This study compares healthcare providers' perceptions of the revised statements to those currently used in vaccine product labelling information.

METHODS

A 30-item online survey with qualitative and quantitative components was distributed to Canadian maternal healthcare providers via professional organizations and public health. Participants read excerpts from revised and existing IIV and Tdap product labelling information and answered questions about how they perceived the safety and effectiveness of the vaccines, whether they would recommend each vaccine during pregnancy, and which statements they preferred.

RESULTS

From June to August 2018, 449 healthcare providers completed the survey, including physicians (45%), nurses (24%), midwives (27%) and others (5%). Most participants perceived the vaccines to be safe and effective based on the revised statements. Over twice as many participants said they would recommend the IIV and Tdap vaccines in pregnancy based on the revised rather than the existing statements (64% versus 21% for IIV and 63% versus 27% for Tdap). Most participants selected that the revised statements better explained the risks and benefits of vaccination in pregnancy (65% versus 21% for IIV; 51% versus 27% for Tdap). Qualitative comments highlighted the strengths of the revised statements and areas for improvement.

CONCLUSIONS

The majority of participants demonstrated preferences for the revised IIV and Tdap product label statements over the existing statements. Comments suggested the revised statements include improvements to the evidence-base and readability. Involving stakeholders improved the development of product labelling information, but further improvement is needed to support the evidence-based use of vaccines in pregnancy.

Aerobic Vaginitis Induced by Escherichia coli Infection During Pregnancy Can Result in Adverse Pregnancy Outcomes Through the IL-4/JAK-1/STAT-6 Pathway

Aerobic vaginitis (AV) can occur if normal vaginal microflora are dominated by aerobic bacteria, seriously affects not only female health, but also fetal health while they are pregnant. Besides, pregnant status also aggravates the symptoms and consequences of the infection. Here, we infected pregnant BALB/c mice with Escherichia coli on embryonic day 4.5 (E4.5) (study group), and administered an equivalent volume of phosphate-buffered saline in another cohort of pregnant mice (control group). We recorded the weight of pregnant mice and their fetuses. The maternal and fetal weight of the study group decreased in comparison with that of the control group, whereas the weight of placenta increased in the study group. Then, five genes with significant upregulation and 15 genes with downregulation were screened. Expression of interleukin 4 (IL-4) mRNA in the study group decreased to 18.5%. Enzyme-linked immunosorbent assay results showed IL-4 expression in mouse plasma declined in the study group at E11.5 and E18.5. mRNA expression of chemokine (c-c motif) ligand (CCL)-17, CCL-22, CCL-24, IL-4, Janus Kinase (JAK)-1, signal transducer and activator of transcription (STAT)-6, and GATA-3 showed significant downregulation in placental and uterine tissues. Flow cytometry of primary decidual macrophages (DMs) revealed more M1-like macrophages in the study group. And after addition of IL-4 to DMs, more M1 macrophages polarized to M2 type macrophages. We did not discover bacteria existed in mouse placentas. Our study affords a feasible method for exploring and managing AV during pregnancy.