Tetanus, diphtheria, and acellular pertussis vaccination during pregnancy and reduced risk of infant acute respiratory infections

Timing of pertussis vaccination during pregnancy: Evidence and implementation - A systematic review

BACKGROUND

Pertussis vaccination in pregnancy has been introduced in an increasing number of countries to better protect infants against the disease in their first weeks of life. The optimal timing of pertussis vaccination in pregnancy is however still under debate.

METHODS

We systematically reviewed published literature on safety, immunogenicity and effectiveness of pertussis vaccination in pregnancy related to timing of vaccination. The search was conducted using PubMed, MEDLINE and Web of Science and yielded 1623 articles, thereof 777 duplicates. Screening resulted in the inclusion of 45 publications reporting on safety (n = 11), immunogenicity (n = 26) and/or effectiveness (n = 9). We also mapped pertussis recommendations in pregnancy by government institutions globally according to the recommended timing of vaccination.

RESULTS

Overall, the selected publications did not indicate increased safety concerns associated with timing of pertussis vaccination in pregnancy. Immunogenicity studies often suggested optimal protection at birth after early third trimester vaccination. Few studies investigated qualitative antibody characteristics, and none investigated antibody titers in breastmilk or cellular-mediated immunity related to timing of vaccination. Effectiveness studies showed decreased vaccine effectiveness of late third trimester pertussis vaccination compared to vaccination earlier in pregnancy. Worldwide, a general recommendation for pertussis vaccination in pregnancy was found for 58 countries, with as many as 22 different recommended timings registered.

CONCLUSION

The timing of pertussis vaccination in pregnancy seems to impact immunogenicity and vaccine effectiveness, with optimal immune responses at birth suggested following early third trimester vaccination and reduced vaccine effectiveness of late third trimester pertussis vaccination suggested compared to vaccination earlier in pregnancy. However, inconsistent and lacking data are reflected in the divergent national recommendations for pertussis vaccination in pregnancy worldwide.

SUMMARY

Pertussis vaccination in pregnancy aims to protect infants in their first weeks of life. Our review suggests that immunogenicity and vaccine effectiveness are impacted by the timing of vaccination in pregnancy. National recommendations for pertussis vaccination in pregnancy vary widely worldwide.

The PRotective Effect of Maternal Immunisation on preTerm birth: characterising the Underlying mechanisms and Role in newborn immune function: the PREMITUR study protocol

Maternal immunisation, a low cost and high efficacy intervention is recommended for its pathogen specific protection. Evidence suggests that maternal immunisation has another significant impact: reduction of preterm birth (PTB), the single greatest cause of childhood morbidity and mortality globally. Our overarching question is: how does maternal immunisation modify the immune system in pregnant women and/or their newborn to reduce adverse pregnancy outcomes and enhance the newborn infant's capacity to protect itself from infectious diseases during early childhood? To answer this question we are conducting a multi-site, prospective observational cohort study collecting maternal and infant biological samples at defined time points during pregnancy and post-partum from nulliparous women. We aim to enrol 400 women and determine the immune trajectory in pregnancy and the impact of maternal immunisation (including influenza, pertussis and/or COVID-19 vaccines) on this trajectory. The results are expected to identify areas that can be targeted for future intervention studies.

A phase 2 randomized controlled dose-ranging trial of recombinant pertussis booster vaccines containing genetically inactivated pertussis toxin in women of childbearing age

BACKGROUND

A phase 2 randomized-controlled safety and immunogenicity trial evaluating different doses of recombinant acellular pertussis vaccine containing genetically-inactivated pertussis toxin (PTgen) was conducted in women of childbearing age in Thailand to identify formulations to advance to a trial in pregnant women.

METHODS

A total of 250 women were randomized 1:1:1:1:1 to receive one dose of one of three investigational vaccines including low-dose recombinant pertussis-only vaccine containing 1 μg PTgen and 1 μg FHA (ap1gen), tetanus, reduced-dose diphtheria (Td) combined to ap1gen (Tdap1gen) or combined to recombinant pertussis containing 2 μg PTgen and 5 μg FHA (Tdap2gen), or one dose of licensed recombinant TdaP vaccine containing 5 μg PTgen and 5 μg FHA (Boostagen®, TdaP5gen) or licensed Tdap vaccine containing 8 μg of chemically inactivated pertussis toxoid (PTchem), 8 μg FHA, and 2.5 μg pertactin (PRN) (BoostrixTM, Tdap8chem). Serum Immunoglobulin G (IgG) antibodies against vaccine antigens were measured before and 28 days after vaccination by ELISA. To advance to a trial in pregnant women, formulations had to induce a PT-IgG seroresponse rate with a 95% confidence interval (95% CI) lower limit of ≥ 50%.

RESULTS

Between 5 and 22 July 2018, a total of 250 women with median age of 31 years were enrolled. Post-vaccination PT-IgG seroresponse rates were 92% (95% CI 81-98) for ap1gen, 88% (95% CI 76-95) for Tdap1gen, 80% (95% CI 66-90) for Tdap2gen, 94% (95% CI 83-99) for TdaP5gen, and 78% (95% CI 64-88) for Tdap8chem. Frequencies of injection site and systemic reactions were comparable between the groups. No serious adverse events were reported during the 28-day post-vaccination period.

CONCLUSIONS

All recombinant acellular pertussis vaccines were safe and immunogenic in women of childbearing age, and all met pre-defined immunogenicity criteria to advance to a trial in pregnant women.

CLINICAL TRIAL REGISTRATION

Thai Clinical Trial Registry, TCTR20180321004.

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.

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.

Clinical repercussions in pertussis infants post-Tdpa vaccination of pregnant woman: An immunization success?

INTRODUCTION

In 2014, there was an epidemic of pertussis in Brazil that caused the death of 129 infants. To control the disease amongst infants under 6 months of age, and especially those under 2 months, the Brazilian Ministry of Health introduced Tdap immunization for all pregnant women.

METHODS

This study aimed to describe the morbidity and mortality variables of pertussis cases in 969 infants aged under 6 months, comparing the periods before and after the introduction of Tdap vaccine in pregnant women. Data was extracted from the Information System on Notifiable Diseases (SINAN) including every case of pertussis that occurred in the metropolitan region of Recife-Brazil in infants under 6 months from January 2009 to October 2018. In order to analyze the variables, patients were divided into two groups Pre-Tdap(2009-2014), and Post-Tdap (2016-2018).

RESULTS

There were no significant differences between the age groups and gender distribution in the period compared. In the Post- Tdap group compared with the Pre-Tdap group, the clinical presentation of pertussis in infants differed with more paroxysmal cough, and more vomiting, less apnea, and cyanosis. During this period, there were fewer complications and no deaths occurred.

CONCLUSIONS

Maternal immunization with Tdap decreased disease severity, complication rates, and no deaths occurred in infants under 6 months of age diagnosed with pertussis.

Infant immunity against viral infections is advanced by the placenta-dependent vertical transfer of maternal antibodies

Neonatal passive immunity, derived from transplacental transfer of IgG antibodies from mother to fetus during pregnancy, can mitigate the risk for severe infections in the early postnatal period. Understanding the placenta as the gateway organ in this process, we aimed to evaluate the influence of specific factors modulating the transplacental IgG transfer rate (TPTR) in 141 mother/neonate pairs. We further evaluated the potential health advantage elicited by maternal IgG with regard to respiratory tract infections during infancy and early childhood. Data and biological samples collected within the prospective longitudinal pregnancy cohort study PRINCE (Prenatal Identification of Children's Health) were used for these analyses. We tested IgG antibody levels against seven pathogens (measles, mumps, rubella, tetanus, diphtheria, pertussis and influenza A) by ELISA and detected seropositivity in 72.6-100% of pregnant women and in 76.3-100% of their neonates, respectively. Cord blood IgG levels reached 137-160% of levels detected in maternal blood. Strikingly, assessment of TPTR for all seven antigens highlighted that TPTR strongly depends on individual placental function. Subsequent in-depth analysis of anti-influenza A IgG revealed a link between cord blood levels and uterine perfusion, measured by uterine artery pulsatility index. Moreover, higher cord blood anti-influenza A IgG levels were associated with a significantly reduced risk for respiratory tract infections during the first six months of life, indicating a high degree of cross-reactivity and possible pathogen-agnostic effects of anti-influenza A antibodies. Taken together, our data suggest that early life immunity is modulated by maternal IgG levels and individual placental features such as perfusion. Vaccination of pregnant women, i.e. against influenza, can increase neonatal antibody levels and hereby protect against early life respiratory infections. Consequently, specific guidelines should evolve in order to safeguard neonates born from pregnancies with poorer placental capacity for vertical transfer of protective antibodies.

Japanese encephalitis vaccination in pregnancy among U.S. active duty military women

INTRODUCTION

Japanese encephalitis (JE) vaccine is an inactivated vaccine that has shown no risks in pregnancy in animal models, but epidemiologic studies are lacking. U.S. military service members located in JE endemic regions are required to be vaccinated; understanding the potential adverse events (AEs), including AEs that may occur in pregnancy, is needed. Here, we assessed pregnancy and infant health outcomes in association with JE vaccination in pregnancy.

METHODS

The study population consisted of 192,570 pregnancies to active duty women (2003-2014), captured in the Department of Defense Birth and Infant Health Research program. JE vaccine in pregnancy, vaccine count, formulation, trimester, and whether first career dose coincided with pregnancy were compared with unexposed pregnancies to assess risk of pregnancy and infant health outcomes. Adjusted risk estimates and 95% confidence intervals (CIs) were calculated by multivariable models.

RESULTS

Of the 192,570 identifed pregnancies, 513 were exposed to the JE vaccine; 474 exposures occurred in the first trimester. For all outcomes, elevated risk estimates ranging from 1.53 to 1.70, were observed with receipt of >1 JE vaccine in pregnancy, though 95% CIs were wide and encompassed the null. First dose of JE vaccination in pregnancy was associated with a 1.87 (95% CI: 1.12-3.13) times increased risk of low birthweight (LBW) when excluding pregnancies exposed to other non-routinely recommended vaccinations in pregnancy. All other associations were null in both main and subset analyses.

CONCLUSIONS

The overall results of these analyses provide reassuring findings for the safety of JE vaccination in pregnancy. Higher counts of JE vaccine received in pregnancy yielded large yet non-statistically significant risk estimates for all outcomes, though likely driven by lack of pregnancy awareness. An association was observed with LBW in subset analyses, but it was limited to women receiving their first JE vaccine and not observed in the larger main analyses.

Safety of tetanus, diphtheria, and acellular pertussis vaccination among pregnant active duty U.S. military women

BACKGROUND

The tetanus, diphtheria, and acellular pertussis (Tdap) vaccine was approved for U.S. adults in 2005 and recommended for administration in every pregnancy in 2012, with optimal timing between 27 and 36 weeks' gestation. In the military, however, a current Tdap vaccination status is compulsory for service, and active duty women may be inadvertently exposed in early pregnancy. Safety data in this population are limited.

OBJECTIVES

To assess safety of inadvertent (0-13 weeks' gestation) and recommended (27-36 weeks' gestation) exposure to the Tdap vaccine in pregnancy.

METHODS

Pregnancies and live births from Department of Defense Birth and Infant Health Research program data were linked with military personnel immunization records to determine pregnancy Tdap vaccine exposure among active duty women, 2006-2014. Multivariable Cox and generalized linear regression models estimated associations between Tdap vaccine exposure and adverse pregnancy or infant outcomes.

RESULTS

Of 145,883 pregnancies, 1272 were exposed to the Tdap vaccine in the first trimester and 9438 between 27 and 36 weeks' gestation. Neither inadvertent nor recommended vaccine exposure were associated with spontaneous abortion, preeclampsia, or preterm labor. Among 117,724 live born infants, 984 were exposed to the Tdap vaccine in the first trimester and 9352 between 27 and 36 weeks' gestation. First trimester exposure was not associated with birth defects, growth problems in utero, growth problems in infancy, preterm birth, or low birth weight. Tdap vaccine exposure between 27 and 36 weeks' gestation was not associated with any adverse infant outcome.

CONCLUSIONS

Among a population of active duty women in the U.S. military who received the Tdap vaccine during pregnancy, we detected no increased risks for adverse maternal, fetal, or infant outcomes. Our findings corroborate existing literature on the safety of exposure to the Tdap vaccine in pregnancy.