Pertussis Antibody Transfer to Preterm Neonates After Second- Versus Third-Trimester Maternal Immunization

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.

Maternal Pertussis Immunization and Immunoglobulin G Levels in Early- to Late-Term and Preterm Infants

Importance

Maternal tetanus, diphtheria, and acellular pertussis (Tdap) vaccination protects newborns against severe pertussis. Data on transplacental antibody transfer on Tdap vaccination before 24 weeks' gestation remain scarce and are particularly relevant for preterm infants to increase the time interval for maternal antibody transfer.

Objective

To assess noninferiority of anti-pertussis toxin (anti-PT) immunoglobulin G (IgG) antibody levels at age 2 months in early- to late-term infants following Tdap vaccination between 20 0/7 and 24 0/7 weeks' gestation compared with 30 0/7 and 33 0/7 weeks' gestation and compared with preterm infants.

Design, Setting, and Participants

This prospective, multicenter cohort study included pregnant women aged 18 years or older in birthing centers and hospitals in the Netherlands between August 2019 and November 2021 who received Tdap vaccination between 20 0/7 and 24 0/7 weeks' gestation. Women with imminent premature birth were recruited if they had received maternal Tdap vaccination between 20 and 24 weeks' gestation. Blood samples were collected from mothers at delivery, from the umbilical cord, and from infants at age 2 months. Data from infants' blood samples at age 2 months were compared with a reference cohort (recruited between January 2014 and February 2016) of early- to late-term infants of the same age whose mothers had received Tdap vaccination between 30 0/7 and 33 0/7 weeks' gestation.

Exposure

Maternal Tdap vaccination between 20 0/7 and 24 0/7 weeks' gestation or 30 0/7 and 33 0/7 weeks' gestation.

Main Outcomes and Measures

The primary outcome was the geometric mean concentration (GMC) of anti-PT IgG antibodies in early- to late-term infants (≥37 0/7 weeks' gestation) at age 2 months, comparing maternal Tdap vaccination between 20 0/7 and 24 0/7 weeks' vs 30 0/7 and 33 0/7 weeks' gestation (reference cohort). Anti-PT GMC in 2-month-old infants born preterm (<35 0/7 weeks' gestation) compared with early- to late-term infants after maternal Tdap vaccination between 20 and 24 weeks' gestation was a secondary outcome.

Results

In total, 221 women who delivered 239 offspring were enrolled in the study; 66 early- to late-term infants (median gestational age [GA], 40.6 weeks [IQR, 39.8-41.0 weeks]; 38 [57.6%] male) and 73 preterm infants (median GA, 32.1 weeks [IQR, 29.5-33.0 weeks]; 42 [54.5%] female) had blood samples collected at 2 months of age. Anti-PT GMC was 14.7 IU/mL (95% CI, 10.6-20.4 IU/mL) in early- to late-term infants following maternal Tdap vaccination between 20 0/7 and 24 0/7 weeks' gestation compared with 27.3 IU/mL (95% CI, 20.1-37.1 IU/mL) in 55 infants in the reference group (median GA, 40.3 [IQR, 39.1-41.0]; 33 [60.0%] female). The mean anti-PT GMC in preterm infants in the study group was 11.2 IU/mL (95% CI, 8.1-15.3 IU/mL) (P = .23 compared with early- to late-term infants).

Conclusions and Relevance

In this cohort study, 2-month-old preterm and early- to late-term infants showed significantly lower anti-PT antibody levels following maternal Tdap vaccination between 20 0/7 and 24 0/7 weeks' gestation compared with 30 0/7 and 33 0/7 weeks' gestation; preterm and early- to late-term infants had similar anti-PT antibody levels, but both groups showed significantly lower antibody levels compared with the reference group. Epidemiological research should investigate whether maternal Tdap vaccination before 24 weeks' gestation provides sufficient protection against clinical pertussis, particularly in preterm infants, as long as no correlate of protection is available.

HIV-related immune activation attenuates polyfunctional IgG and memory B-cell responses to Tdap immunization during pregnancy

BACKGROUND

Maternal pertussis vaccination with Tdap vaccine is recommended to protect newborns from severe postnatal infection. HIV-exposed uninfected (HEU) infants have a higher incidence of pertussis infection and may particularly benefit from maternal immunization. The impact of HIV infection on the quality of IgG and memory B cell (MBC) responses to Tdap vaccination in pregnant women (PW) living with HIV (PWH) is unknown.

METHODS

In this observational study, humoral immune responses to Tdap vaccination, including IgG levels, Fc-dependent effector functions, and MBC frequencies, were measured before and after vaccination in 40 PWH and 42 HIV-uninfected PW. Placental transfer of IgG and avidity were assessed in cord blood (CB). Soluble and cellular immune activation markers were quantified at baseline.

FINDINGS

One month after vaccination, PWH had lower frequencies of MBC compared with HIV-uninfected PW. At delivery, PWH had attenuated pertussis-specific IgG levels and Fc-dependent effector functions. Reduced levels of maternal vaccine polyfunctional IgG and IgG avidity were transferred to HEU as compared to HIV-unexposed newborns. After adjustment with ethnicity, maternal antibody levels and gestational age at vaccination, HIV infection was independently associated with decreased levels of PT specific-IgG in CB. Both maternal and neonatal pertussis-specific IgG responses as well as PT-specific IgG avidity were inversely correlated with maternal sCD14 levels before vaccination among PWH.

INTERPRETATION

Maternal HIV infection is associated with attenuated humoral immune responses to Tdap vaccination that correlate with sCD14. Suboptimal transfer of maternal immunity may further increase the risk of severe pertussis infection in HEU infants.

FUNDING

This work was supported by IRIS Fund managed by the Foundation Roi Baudouin [2017J1820690206902], Association Vésale pour la Recherche Médicale and the Medical Council of CHU Saint-Pierre and has been funded in part with Federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, US Department of Health and Human Services, under Award No. U19AI145825. N.D. is a clinical researcher and A.M. is Research Director at the Fonds de la Recherche Scientifique (F.R.S.-FNRS), Belgium. M.E.A. was partially supported by NIHNIAID1U19AI14825. This article is published with the support of the Fondation Universitaire of Belgium.

Effective and safe transfer of maternal antibodies persisting two months postpartum following maternal immunization with different doses of recombinant pertussis-containing vaccines

INTRODUCTION

Recombinant acellular pertussis (ap) vaccines containing genetically inactivated pertussis toxin (PTgen) and filamentous hemagglutinin (FHA) with or without tetanus (TT) and diphtheria (DT) vaccines (Td) were found safe and immunogenic in non-pregnant and pregnant women. We report here maternal antibody transfer and safety data in mothers and neonates.

METHODS

This is the follow up of a phase 2 trial in 2019 among 400 pregnant women who randomly received one dose of recombinant pertussis-only vaccine containing 1 µg PTgen and 1 µg FHA (ap1gen), or Td combined with ap1gen (Tdap1gen), or with 2 µg PTgen and 5 µg FHA (Tdap2gen), or with 5 µg PTgen and 5 µg FHA (TdaP5gen, Boostagen®, BioNet, Thailand) or chemically-inactivated acellular pertussis comparator (Tdap8chem, Boostrix™, GSK, Belgium), either in the second or third trimester of gestation. IgG against PT, FHA, TT and DT were assessed by ELISA, PT-neutralizing antibodies (PTNA) by Chinese Hamster Ovary cell assay and safety outcomes at delivery in mothers and at birth.

RESULTS

Anti-PT and anti-FHA geometric mean concentration (GMC) ratio between infants at birth and mothers at delivery was above 1 in all groups. PT GMC in infants at birth were ≥30 IU/mL in all groups with the highest titers in infants found in TdaP5gen group at birth (118.8 [95% CI 93.9-150.4]). At 2 months, PT GMC ratio to Tdap8chem (98.75% CI) was significantly higher for TdaP5gen (2.6 [1.7-4.0]) and comparable for other recombinant vaccines. No difference in PTNA titers at birth was observed between all groups nor between time of vaccination. Adverse events were comparable in all vaccine groups.

CONCLUSIONS

BioNet licensed (TdaP5gen and Tdap2gen) and candidate vaccines (Tdap1gen and ap1gen) when given to pregnant women in the second or third trimester of gestation are safe and have induced passive pertussis immunity to infants.

Influence of Timing of Maternal Pertussis Immunization on the Avidity of Transferred Antibodies in Term and Preterm Neonates

The timing of maternal pertussis vaccination influences the titers of cord-blood anti-pertussis antibodies. Whether it affects their avidity is unknown. We demonstrate in 298 term and 72 preterm neonates that antibody avidity is independent of the timing of maternal vaccination, whether comparing second with third trimester or intervals before birth.

Maternal vaccination: shaping the neonatal response to pertussis

Antepartum maternal vaccination can protect highly sensitive newborns before they are old enough to receive their own vaccines. Two vaccines are currently recommended during pregnancy: the flu vaccine and the Tdap vaccine against tetanus, diphtheria, and pertussis. Although there is strong evidence that maternal vaccination works to protect the offspring, limitations in the understanding of vaccines and of maternal transfer of immunity compound to obscure our understanding of how they work. Here we focus on the example of pertussis to explore the possible mechanisms involved in the transfer of protection to offspring and how these may impact the newborn's response to future exposure to pertussis. For example, Tdap vaccines induce pathogen specific antibodies, and those antibodies are known to be transferred from mother to the fetus in utero and to the newborn via milk. But antibodies alone have modest impact on pertussis disease, and even less effect on colonization/transmission. Maternal immune cells can also be transferred to offspring and may play a direct role in protection from disease and/or influence the developing neonatal immune system. However, some of the transferred immunity may also blunt the offspring's response to subsequent vaccination. In this review we will summarize the protection conferred to offspring by maternal vaccination against pertussis and the likely mechanisms by which protection is transferred, identifying the many knowledge gaps that limit our most effective application of this approach.

Socio-psychological determinants of second trimester maternal pertussis vaccination acceptance in the Netherlands

BACKGROUND

A maternal tetanus-diphtheria-and-acellular-pertussis (Tdap) vaccine is offered to all pregnant women in the Netherlands in their second trimester since December 2019. However, former studies solely investigated the socio-psychological factors that influence vaccine acceptance among pregnant women in the third trimester. We identified predicting factors for attitude, intention and acceptance of maternal Tdap vaccination during the second trimester of pregnancy.

METHODS

As part of a large prospective cohort study, women early in pregnancy completed a questionnaire on determinants regarding acceptance of maternal Tdap vaccination between 20 and 24w of gestation. The vaccine was offered after completion of the questionnaire. A random forest model and Receiver Operating Characteristics (ROC) analyses were carried out to identify the factors most predictive for vaccine acceptance on the whole data set, and also in sensitivity analysis on a subset reflecting the annual nationwide 70% vaccination uptake.

RESULTS

Among 1158 participants who were offered a Tdap vaccination between 20 and 24w of gestation, 1098 (94.8%) accepted and 60 (5.2%) rejected the vaccine. Random forest analyses identified intention as most predictive for acceptance, followed by attitude towards vaccination, beliefs regarding safety, risk perception of severity of side effects, moral responsibility, beliefs regarding effectiveness and risk perception of susceptibility of side effects, with a sensitivity of 100% and a specificity of 40%, for which this combination could be improved by the ROC analysis to 82% and 67%, respectively. The sensitivity analysis yielded an order of predictors that generally corresponded with the initial model.

CONCLUSIONS

Intention, attitude, beliefs on safety and effectiveness, risk perception of side effects and moral responsibility were most predictive for maternal Tdap vaccine acceptance during the second trimester of pregnancy, in accordance with studies regarding third trimester vaccination. These should be discussed by healthcare professionals early in pregnancy to provide an informed choice towards vaccine acceptance.

Optimization of Timing of Maternal Pertussis Immunization From 6 Years of Postimplementation Surveillance Data in England

BACKGROUND

England's third-trimester maternal pertussis vaccination, introduced in October 2012, was extended to the second trimester in 2016. Maternal vaccination provides high protection against infant disease, but routine second-trimester vaccination has not previously been assessed.

METHODS

National laboratory-confirmed pertussis case surveillance determined vaccination history, maternal vaccination history and hospitalization. Pertussis hospital admissions between 2012 and 2019 were extracted from the Hospital Episode Statistics data set. Vaccine effectiveness (VE) was calculated for pertussis case patients born between October 2012 and September 2018 using the screening method and matching with a nationally representative data set.

RESULTS

Higher coverage was observed after earlier maternal vaccination with approximately 40% of pregnant women vaccinated ≥13 weeks before delivery. Cases and hospitalizations stabilized at low levels in younger infants but remained elevated in older infants, children, and adults. No deaths occurred in infants with vaccinated mothers after 2016. Of 1162 laboratory-confirmed pertussis cases in the study, 599 (52%) were in infants aged <93 days: 463 (77%) with unvaccinated and 136 (23%) with vaccinated mothers. The VE was equivalent in infants with mothers vaccinated at different gestational periods except in those with mothers vaccinated between 7 days before and 41 days after delivery. Children whose mothers were unvaccinated but with vaccination in a previous pregnancy had a VE against disease of 44% (95% confidence interval, 19%-75%). There was no increased disease risk after primary vaccination in children with mothers vaccinated at least 7 days before delivery.

CONCLUSIONS

National policy recommending vaccination in the second trimester increased earlier maternal vaccine uptake with sustained high VE and impact against early infant disease.

Vaccination in Pregnancy against Pertussis: A Consensus Statement on Behalf of the Global Pertussis Initiative

Infants are at high risk for severe morbidity and mortality from pertussis disease during early infancy. Vaccination against pertussis in pregnancy has emerged as the ideal strategy to protect infants during these early, vulnerable, first months of life. On 30 November and 1 December 2021, the Global Pertussis Initiative held a meeting that aimed to discuss and review the most up-to-date scientific literature supporting vaccination against pertussis in pregnancy and outstanding scientific questions. Herein, we review the current and historically published literature and summarize the findings as consensus statements on vaccination against pertussis in pregnancy on behalf of the Global Pertussis Initiative.

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.

Clinical Risk Factors Associated With Late-Onset Invasive Group B Streptococcal Disease: Systematic Review and Meta-Analyses

BACKGROUND

Group B streptococcal (GBS) infection remains one of the most significant causes of late-onset sepsis and meningitis (LOGBS) among young infants. However, transmission routes and risk factors for LOGBS are not yet fully understood.

METHODS

We conducted systematic reviews on clinical risk factors previously reported in the literature (prematurity, low birth weight [<2500 g], antenatal colonization, multiple-gestation pregnancy, maternal age <20 years, male infant sex, intrapartum fever, prolonged rupture of membranes) and meta-analyses to determine pooled estimates of risk.

RESULTS

We included 27 articles, reporting 5315 cases. Prematurity (odds ratio [OR] 5.66; 95% confidence interval [CI]: 4.43-7.22), low birth weight (OR 6.73; 95% CI: 4.68-9.67), maternal colonization (2.67; [2.07-3.45]), and multiple-gestation pregnancies (OR 8.01; 95% CI: 5.19-12.38) were associated with an increased risk of LOGBS.

CONCLUSIONS

Prematurity/low birth weight and maternal colonization are major risk factors for LOGBS. Future GBS vaccine studies should try to establish the optimal time for vaccination during pregnancy to protect preterm infants.

Missed pertussis diagnosis during co-infection with Bordetella holmesii

The purpose of this study is to identify predictive factors associated with missed diagnosis of B. pertussis-B. holmesii co-infection by assessing the analytical performance of a commercially available multiplexed PCR assay and by building a prediction model based on clinical signs and symptoms for detecting co-infections. This is a retrospective study on the electronic health records of all clinical samples that tested positive to either B. pertussis or B. holmesii from January 2015 to January 2018 at Geneva University Hospitals. Multivariate logistic regression was used to build a model for co-infection prediction based on the electronic health record chart review. Limit of detection was determined for all targets of the commercial multiplexed PCR assay used on respiratory samples. A regression model, developed from clinical symptoms and signs, predicted B. pertussis and B. holmesii co-infection with an accuracy of 82.9% (95% CI 67.9-92.8%, p value = .012), for respiratory samples positive with any of the two tested Bordetella species. We found that the LOD of the PCR reaction targeting ptxS1 is higher than that reported by the manufacturer by a factor 10. The current testing strategy misses B. pertussis and B. holmesii co-infections by reporting only B. holmesii infections. Thus, we advocate to perform serological testing for detecting a response against pertussis toxin whenever a sample is found positive for B. holmesii. These findings are important, both from a clinical and epidemiological point of view, as the former impacts the choice of antimicrobial drugs and the latter biases surveillance data, by underestimating B. pertussis infections during co-infections.

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.

[Should French pregnant women be vaccinated against pertussis during pregnancy?]

Many countries with a high perinatal level have started a policy of vaccination of pregnant women against pertussis. To date, France has not chosen this policy. The objective was to review knowledge on pertussis mortality in infants. Compare the strategies available to protect the infant before his first vaccination, scheduled for two months of age. We proceeded to a litterature analysis, from January 1998 to 2021. Search by the following keywords used ; "Whooping cough, vaccination, pregnancy, strategy, cocooning", on the scientific basis of "Pubmed", as well as French and foreign vaccination recommendations. Currently 90% of whooping cough deaths are concerning infants under six months of age and this mortality represents 2% of mortality in the first year of life. Vaccination at birth is not effective. The cocooning strategy, which consists of vaccinating those around the child, is expensive and difficult to implement. A systematic vaccination policy for pregnant women is effective and reasonably expensive when compared to the cocooning strategy. In England, it was recently accompanied by a 78% reduction in confirmed cases of pertussis in infants under six months of age. In conclusion, compared to cocooning strategy, pertussis vaccination of pregnant women appears more effective and cost-effective, and this with each pregnancy.

Flu and pertussis vaccination during pregnancy in Geneva during the COVID-19 pandemic: A multicentric, prospective, survey-based study

Objective

Methods

Results

Conclusions

No evidence of fetal defects or anti-syncytin-1 antibody induction following COVID-19 mRNA vaccination

The impact of Coronavirus Disease 2019 (COVID-19) mRNA vaccination on pregnancy and fertility has become a major topic of public interest. We investigated 2 of the most widely propagated claims to determine (1) whether COVID-19 mRNA vaccination of mice during early pregnancy is associated with an increased incidence of birth defects or growth abnormalities; and (2) whether COVID-19 mRNA-vaccinated human volunteers exhibit elevated levels of antibodies to the human placental protein syncytin-1. Using a mouse model, we found that intramuscular COVID-19 mRNA vaccination during early pregnancy at gestational age E7.5 did not lead to differences in fetal size by crown-rump length or weight at term, nor did we observe any gross birth defects. In contrast, injection of the TLR3 agonist and double-stranded RNA mimic polyinosinic-polycytidylic acid, or poly(I:C), impacted growth in utero leading to reduced fetal size. No overt maternal illness following either vaccination or poly(I:C) exposure was observed. We also found that term fetuses from these murine pregnancies vaccinated prior to the formation of the definitive placenta exhibit high circulating levels of anti-spike and anti-receptor-binding domain (anti-RBD) antibodies to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) consistent with maternal antibody status, indicating transplacental transfer in the later stages of pregnancy after early immunization. Finally, we did not detect increased levels of circulating anti-syncytin-1 antibodies in a cohort of COVID-19 vaccinated adults compared to unvaccinated adults by ELISA. Our findings contradict popular claims associating COVID-19 mRNA vaccination with infertility and adverse neonatal outcomes.

Comprehensive Overview of Vaccination during Pregnancy in Europe

Vaccinations during pregnancy can protect the mother from several infections, thus blocking vertical transmission. Furthermore, through passive antibody transfer, the newborn can be protected against some infections in the first months of life until their own vaccination regimen is initiated and completed at the appropriate age. Pregnancy can be considered a high-risk condition that increases vulnerability to infectious diseases with potentially unfavorable evolution. We present the current knowledge on vaccination during pregnancy in Europe as a useful information source for different health workers involved in prenatal care. Many European countries implement vaccination policies specifically designed for pregnant women, but there is great heterogeneity among programs. Recommendations on vaccination during pregnancy must be based on current high-quality scientific data. The decisions must be made for each individual case, depending on the associated conditions or special circumstances, with a concomitant assessment of the potential benefits and risks to both the pregnant patient and the fetus. Many vaccines are well-tolerated in pregnant women, with no clinically meaningful injection site reactions, systemic symptoms, or vaccine-related serious adverse events.

Study protocol of the PIMPI-project, a cohort study on acceptance, tolerability and immunogenicity of second trimester maternal pertussis immunization in relation to term and preterm infants

Background

Maternal immunization confers passive immunity to the fetus by transplacental antibody transfer. Infants may be better protected against pertussis if the mother received a diphtheriae, tetanus and acellular pertussis (Tdap) vaccination in the second trimester of pregnancy compared to the third trimester. This study evaluates IgG antibody concentrations in term and preterm infants at birth and 2 months after birth after maternal Tdap-vaccination between 20⁰ and 24⁰ w of gestation vs third trimester Tdap-vaccination. Further aims are assessing the determinants that underlie acceptance of second trimester maternal Tdap-vaccination as well as the tolerability of vaccination.

Methods

This prospective cohort study consists of two parts. In the acceptance part, pregnant women complete a questionnaire on determinants that underlie acceptance of a second trimester Tdap-vaccination, which is offered subsequently between 20⁰ and 24⁰ w of gestation. Vaccinated women complete an additional questionnaire on vaccination tolerability. Vaccinated women may also participate in the immunogenicity part, in which blood is drawn from mother at delivery and from infant at birth and 2 months after birth. Women are also eligible for the immunogenicity part if they received a Tdap-vaccination between 20⁰ and 24⁰ w of gestation via the national immunization program and get hospitalized for an imminent preterm delivery. Blood sampling continues until 60 term and 60 preterm mother-infant-pairs have been included. Pertussis-specific IgG antibody concentrations are determined in serum using a fluorescent bead-based multiplex immunoassay. For term infants, non-inferiority in IgG antibody concentrations against pertussis toxin (anti-PT) will be assessed referred to a historical control group in which mothers were Tdap-vaccinated between 30⁰ and 32⁰ w of gestation. For preterm infants, non-inferiority of anti-PT IgG concentrations is referred to as 85% of infants having ≥ 20 international units/mL at 2 months after birth.

Discussion

This study investigates acceptance, tolerability and immunogenicity regarding maternal Tdap-immunization between 20⁰ and 24⁰ w of gestation. Its results provide insight into the effects of second trimester Tdap-vaccination on IgG antibody concentrations in term and preterm infants before primary infant vaccinations. Results on acceptance and tolerability guide antenatal care providers in communication with pregnant women and maintain the safety of second trimester Tdap-vaccination.

Trial registration: EU Clinical Trials Register, 2018-002976-41, retrospectively registered 24 July 2019, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2018-002976-41.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06559-w.

Effectiveness of maternal pertussis vaccination in protecting newborn: A matched case-control study

INTRODUCTION

The objective was to estimate the effectiveness of maternal pertussis vaccination in protecting infants aged < 2 months.

METHODS

We performed a case-control study. Laboratory-confirmed cases aged <8 weeks at disease onset were identified and 2-4 matched-controls born within ± 15 days of the case were included. Information was obtained from healthcare providers and maternal interviews. Odds ratios (OR) were calculated using multivariable conditional logistic regression. Vaccine effectiveness (VE) was estimated as (1 - OR) × 100%.

RESULTS

47 cases and 124 controls were studied. The mean age (in days) (39.8 ± 12.7 vs. 40.8 ± 13.2), weeks of gestation (38.8 vs. 39.1, p = 0.43) and mean birth weight (3.309 vs. 3.253 kg, p = 0.55) were comparable between cases and controls. Mothers of cases were less frequently vaccinated in the third trimester (59.6% vs. 83.9%, p <0.001). The VE of maternal vaccination in pregnancy was 88.0% (95%CI 53.8% -96.5%), and was slightly higher in those vaccinated before the 32nd week of gestation (88.5% vs 87.8%).

CONCLUSION

Pertussis vaccination in pregnancy is very effective in reducing pertussis in children aged < 2 months. Vaccination before and after the 32nd week of pregnancy are equally effective in reducing the risk of pertussis.

Safety, immunogenicity, and transplacental antibody transport of conjugated and polysaccharide pneumococcal vaccines administered to pregnant women with HIV: a multicentre randomised controlled trial

BACKGROUND

Pneumococcus remains an important cause of morbidity in pregnant women with HIV and their infants. We compared the safety and immunogenicity of PCV-10 and PPV-23 with placebo administered in pregnancy.

METHODS

This double-blind, multicentre, randomised controlled trial was done at eight outpatient clinics in Brazil. Eligible participants were adult women with HIV who were pregnant at a gestational age between 14 weeks and less than 34 weeks and who were taking antiretroviral therapy at study entry. Participants were randomly assigned (1:1:1) to receive either PCV-10, PPV-23, or placebo. Participants and study teams were unaware of treatment allocation. Antibodies against seven vaccine serotypes in PCV-10 and PPV-23 were measured by ELISA. The primary outcomes were maternal and infant safety assessed by the frequency of adverse events of grade 3 or higher; maternal seroresponse (defined as ≥2-fold increase in antibodies from baseline to 28 days after immunisation) against five or more serotypes; and infant seroprotection (defined as anti-pneumococcus antibody concentration of ≥0·35 μg/mL) against five or more serotypes at 8 weeks of life. The study was powered to detect differences of 20% or higher in the primary immunological outcomes between treatment groups. This trial is registered with ClinicalTrials.gov, NCT02717494.

FINDINGS

Between April 1, 2016, and Nov 30, 2017, we enrolled 347 pregnant women with HIV, of whom 116 were randomly assigned to the PCV-10 group, 115 to the PPV-23 group, and 116 to the placebo group. One participant in the PCV-10 group did not receive the vaccine and was excluded from subsequent analyses. The frequency of adverse events of grade 3 or higher during the first 4 weeks was similar in the vaccine and placebo groups (3% [90% CI 1-7] for the PCV-10 group, 2% [0-5] for the PPV-23 group, and 3% [1-8] for the placebo group). However, injection site and systemic grade 2 adverse reactions were reported more frequently during the first 4 weeks in the vaccine groups than in the placebo group (14% [9-20] for the PCV-10 group, 7% [4-12] for the PPV-23 group, and 3% [1-7] for the placebo group). The frequency of grade 3 or higher adverse effects was similar across maternal treatment groups (20% [14-27] for the PCV-10 group, 21% [14-28] for the PPV-23 group, and 20% [14-27] for the placebo group). Seroresponses against five or more serotypes were present in 74 (65%) of 114 women in the PCV-10 group, 72 (65%) of 110 women in the PPV-23 group, and none of the 113 women in the placebo group at 4 weeks post vaccination (p<0·0001 for PPV-23 group vs placebo and PCV-10 group vs placebo). Seroresponse differences of 20% or higher in vaccine compared with placebo recipients persisted up to 24 weeks post partum. At birth, 76 (67%) of 113 infants in the PCV-10 group, 62 (57%) of 109 infants in the PPV-23 group, and 19 (17%) of 115 infants in the placebo group had seroprotection against five or more serotypes (p<0·0001 for PPV-23 vs placebo and PCV-10 vs placebo). At 8 weeks, the outcome was met by 20 (19%) of 108 infants in the PCV-10 group, 24 (23%) of 104 infants in the PPV-23 group, and one (1%) of 109 infants in the placebo group (p<0·0001). Although a difference of 20% or higher compared with placebo was observed only in the infants who received PPV-23 at 8 weeks of life, the difference between the two vaccine groups was not appreciable.

INTERPRETATION

PCV-10 and PPV-23 were equally safe and immunogenic in pregnant women with HIV and conferred similar levels of seroprotection to their infants. In areas in which childhood PCV administration decreased the circulation of PCV serotypes, PPV-23 administration to pregnant women with HIV might be more advantageous than PCV by virtue of including a broader range of serotypes.

FUNDING

Eunice Kennedy Shriver National Institute of Child Health and Human Development.

TRANSLATION

For the Portuguese translation of the abstract see Supplementary Materials section.

Tetanus, Diphtheria, Acellular Pertussis Vaccination During Pregnancy and Risk of Pertussis in the Newborn in Publicly and Privately Insured Mother-infant Pairs in the United States

BACKGROUND

In the United States, pertussis circulation persists and primarily infects infants and children, despite routine vaccinations. To minimize infant morbidity and mortality from the disease before the first DTaP dose, the Advisory Committee on Immunization Practices recommends maternal Tdap vaccination in weeks 27-36 of pregnancy.

METHODS

Cohorts of mother-infant pairs in the Medicaid Analytic eXtract (MAX) (2010-2014) and IBM MarketScan (2011-2015) databases were analyzed to estimate the effectiveness of prenatal Tdap vaccination compared with no vaccination to prevent infant pertussis in the first 6 months. Hazard ratios were estimated with Cox proportional hazards models and adjusted for potential confounders via inverse probability weights. The impact of preterm delivery on the risk of pertussis was analyzed. Results from the 2 databases were pooled.

RESULTS

In MarketScan, women received Tdap vaccination before delivery in 114,067 (25.6%) of 445,638 pregnancies and in MAX, 33,286 (4.8%) of 695,262 pregnancies. Among pregnancies with preterm delivery, only 21.2% and 3.8% in MarketScan and MAX had been vaccinated. The risk of pertussis in unvaccinated term infants was 3.5 (MarketScan) and 17 (MAX) per 10,000; and in preterm infants, it was 8.4 (MarketScan) and 19.8 (MAX) per 10,000. The pooled hazard ratio for Tdap vaccination any time before delivery versus no vaccination was 0.64 [95% confidence interval (CI): 0.41-1.00]. The hazard ratio was 0.11 (95% CI: 0.03-0.36) for preterm and 0.78 (95% CI: 0.48-1.29) for term infants vaccinated before 37 weeks. The incidence of pertussis was higher and the protective hazard ratio stronger during pertussis outbreaks.

CONCLUSIONS

Prenatal Tdap vaccination reduces the risk of pertussis infections in the infants' first 6 months by 36%. Vaccination soon after 27 weeks of pregnancy, before when deliveries began, ensures vaccination includes those born preterm, who are at highest risk for pertussis and benefit particularly from this vaccination.

Safety and immunogenicity of a prototype recombinant alpha-like protein subunit vaccine (GBS-NN) against Group B Streptococcus in a randomised placebo-controlled double-blind phase 1 trial in healthy adult women

BACKGROUND

Group B Streptococcus (GBS) is the leading cause of life-threatening infections in new-borns and may cause invasive disease, stillbirth and preterm delivery during pregnancy. While no licensed vaccine exists, maternal immunization might protect against neonatal disease and adverse pregnancy outcomes. We assessed the safety and immunogenicity of a prototype vaccine consisting of the fused N-terminal domains of the AlphaC and Rib surface proteins of GBS (GBS-NN).

METHODS

GBS-NN was tested in a randomised, double-blind, placebo-controlled, parallel group, phase I study, in healthy non-pregnant women. A dose-escalation phase, with two doses, four weeks apart, of 10, 50 or 250 µg, administered with or without aluminium hydroxide, was initially assessed (n = 60). This was followed by a dose-confirmation study, where one dose of 100 µg adjuvanted GBS-NN was compared with two doses of either 50 or 100 µg adjuvanted GBS-NN, again administered with four weeks interval between the doses (n = 180). Safety and immunogenicity were monitored for one year.

RESULTS

GBS-NN was well tolerated with some, mostly mild, injection site reactions observed. Adjuvant significantly increased antibody concentrations and the response was boosted by a second dose. The IgG GMCs remained strongly elevated during the whole one-year duration of the study. Maximal responses occurred after two 50 µg doses, resulting in IgG GMC of 16.9 µg/ml at the primary immunological endpoint, twelve weeks after the first dose. For this regimen, 100% and 89% of the subjects achieved antibody levels above the arbitrary thresholds of 1 and 4 µg/ml, respectively. The added beneficial effect of a second dose was most pronounced for subjects with pre-existing IgG levels below the median of the entire cohort.

CONCLUSION

The prototype GBS-NN vaccine was found to be well tolerated and highly immunogenic with an optimal regimen of two doses of 50 µg in the presence of adjuvant. Further development of a maternal vaccine based on the N-terminal domains of the alpha-like protein family of GBS is warranted (NCT02459262).

Optimising the Timing of whooping cough Immunisation in MUMs: a randomised controlled trial investigating the timing of pertussis vaccination in pregnancy (OpTIMUM): a protocol paper

Background: Pertussis is a highly infectious respiratory illness caused by the bacteria Bordetella pertussis. A resurgence of pertussis, even in countries with good vaccine coverage, has led to an increase in infant deaths. In response to this, many countries have introduced pertussis vaccination in pregnancy. This strategy is effective at preventing infant disease, but there remains uncertainty about what gestational timing is best to ensure maximal protection of the infant. These uncertainties are the rationale for this randomised controlled trial and a sub-study investigating pertussis-specific antibody in breastmilk.   Protocol: We will recruit 354 pregnant women and will randomise them to receive their pertussis vaccination in one of three gestational age windows: ≤23+6, 24-27+6 and 28-31+6 weeks of gestation.  Vaccination will be with Boostrix-IPV® and participants will be asked to complete a symptom diary for seven days following vaccination. Blood sampling will be performed prior to vaccination, two weeks following vaccination and at the time of delivery. A cord blood sample will be collected at delivery and a blood sample collected from the infant 4-10 weeks after completion of the primary immunisations. Individuals participating in the breastmilk sub-study will provide a sample of colostrum within 48 hours of delivery and samples of breastmilk at two weeks and around five-six months. Blood samples will be analysed using enzyme linked immunosorbent assay (ELISA) techniques for pertussis toxin, filamentous haemagglutinin and pertactin. A subset of serum samples will also be analysed using a functional assay. Colostrum and breastmilk samples will be analysed using functional assays. Discussion: Although pertussis vaccination has been shown to be safe and effective in pregnancy there remains debate about the optimal timing for the administration during pregnancy. This study will investigate antibody responses in serum and breastmilk when vaccination is performed in three different time periods. Clinicaltrials.gov registration: NCT03908164 (09/04/2019)

Pertussis immunization during pregnancy: assessment of the role of maternal antibodies on immune responses in term and preterm born infants

BACKGROUND

Limited data exist on the impact of maternal Tetanus, Diphtheria, acellular Pertussis (aP) (Tdap) vaccination for preterm born infants. We report its effect at birth and on antibody-mediated immune responses to a DTaP-IPV-HB-PRP~T vaccine in preterm compared to term infants.

METHODS

Women delivering at term or prematurely were either vaccinated with a Tdap vaccine (Boostrix®, GSK) during pregnancy or not vaccinated in the last 5 years. Cord and maternal blood were collected at delivery. Infants were vaccinated with DTaP-IPV-HB-PRP~T vaccine (Hexyon®, Sanofi Pasteur) and bled before and one month after primary (8-12-16 weeks) and before and one month after booster vaccination (13 or 15 months for preterm and term respectively). Immunoglobulin G antibodies against all antigens included in DTaP-IPV-HB-PRP~T vaccine were measured (NCT02511327).

RESULTS

Cord blood Geometric Mean Concentrations (GMCs) in preterm infants from Tdap-vaccinated women were significantly higher than in term and preterm infants from unvaccinated women. A longer time interval between maternal vaccination and delivery resulted in higher cord blood GMCs in preterm infants. Equal GMCs in term and preterm infants from Tdap-vaccinated women were observed after primary vaccination. After boosting, significantly lower GMCs were seen for PT, FHA and TT in preterm compared to term infants from Tdap-vaccinated women, yet still comparable to GMCs in both term and preterm infants from unvaccinated women.

CONCLUSION

Preterm infants profit from maternal Tdap vaccination. Prematurity did not influence primary immune responses in the presence of maternal antibodies, but was associated with a lower booster immune response.

Cost-effectiveness of maternal immunization against neonatal invasive Group B Streptococcus in the Netherlands

BACKGROUND

Neonatal invasive Group B Streptococcus (GBS) infection causes considerable disease burden in the Netherlands. Intrapartum antibiotic prophylaxis (IAP) prevents early-onset disease (EOD), but has no effect on late-onset disease (LOD). A potential maternal GBS vaccine could prevent both EOD and LOD by conferring immunity in neonates.

OBJECTIVE

Explore under which circumstances maternal vaccination against GBS would be cost-effective as an addition to, or replacement for the current risk factor-based IAP prevention strategy in the Netherlands.

METHODS

We assessed the maximum cost-effective price per dose of a trivalent (serotypes Ia, Ib, and III) and hexavalent (additional serotypes II, IV, and V) GBS vaccine in addition to, or as a replacement for IAP. To project the prevented costs and disease burden, a decision tree model was developed to reflect neonatal GBS disease and long-term health outcomes among a cohort based on 169,836 live births in the Netherlands in 2017.

RESULTS

Under base-case conditions, maternal immunization with a trivalent vaccine would gain 186 QALYs and prevent more than €3.1 million in health care costs when implemented in addition to IAP. Immunization implemented as a replacement for IAP would gain 88 QALYs compared to the current prevention strategy, prevent €1.5 million in health care costs, and avoid potentially ~ 30,000 IAP administrations. The base-case results correspond to a maximum price of €58 per dose (vaccine + administration costs; using a threshold of €20,000/QALY). Expanding the serotype coverage to a hexavalent vaccine would only have a limited additional impact on the cost-effectiveness in the Netherlands.

CONCLUSIONS

A maternal GBS vaccine could be cost-effective when implemented in addition to the current risk factor-based IAP prevention strategy in the Netherlands. Discontinuation of IAP would save costs and prevent antibiotic use, however, is projected to lead to a lower health gain compared to vaccination in addition to IAP.

The Potential Role of Nonhuman Primate Models to Better Comprehend Early Life Immunity and Maternal Antibody Transfer

Early life immunity is a complex field of research and there are still gaps in knowledge regarding the detailed mechanism of maternal antibody transfer, the impact of maternal antibodies on infant vaccine responses and the ontogeny of human early life immunity. A comprehensive understanding is necessary to identify requirements for early life vaccines and to improve early childhood immunization. New immunological methods have facilitated performing research in the youngest, however, some questions can only be addressed in animal models. To date, mostly murine models are used to study neonatal and infant immunity since they are well-described, easy to use and cost effective. Given their limitations especially in the transfer biology of maternal antibodies and the lack of infectivity of numerous human pathogens, this opinion piece discusses the potential and prerequisites of the nonhuman primate model in studying early life immunity and maternal antibody transfer.

Vaccination in preterm and low birth weight infants in India

In India, the high neonatal and infant mortality rate is due in part to an increasing number of preterm and low birth weight (LBW) infants. Given the immaturity of immune system, these infants are at an increased risk of hospitalization and mortality from vaccine-preventable diseases (VPDs). In this narrative review, we screened the scientific literature for data on the risk of VPDs, vaccination delay and factors related to it in Indian preterm and LBW infants. Although routine childhood vaccinations are recommended regardless of gestational age or birth weight, vaccination is often delayed. It exposes these infants to a higher risk of infections, their associated complications, and death. After-birth complications, lack of awareness of recommendations, vaccine efficacy and effectiveness and concerns related to safety are some of the common barriers to vaccination. Awareness campaigns might help substantiate the need for (and value of) vaccination in preterm and LBW infants.

What is the context?

In India, the high neonatal mortality rate is due in part to an increasing number of pretern and low birth weight intants.

Affected infants have a poorly developed inmune system and are more susceptible to contracting vaccine-preventable diseases.

The Indian Academy of Pediatrics recommends vaccination according to the same schedule used for full term infants, following chronological (not gestational) age.

Delays in vaccinations increase the risk of preventable infections.

What is new?

Our review of the scientific literature shows that, in India:

infections have more serious conseuences in preterm and low birth weight infants

delays to vaccinate affected infants are common, mostly due to safety and effectiveness concerns from parents and healthcare pracitionrs.

What is the impact?

Improving mternal nutritional status and immunization, and perinatal care could help reduce the number of preterm and low birth weight infants.

Combining maternal immunization with vaccination of affected infants can confer safe and effective protection.

Awareness campaigns for parents and healthcare practitioners could address the issue of vaccination delay in pretern and low birth weight infants in India.

Background incidence rates of adverse pregnancy outcomes in the Netherlands: Data of 2006-2018

OBJECTIVE

Maternal vaccination is an effective and safe intervention to protect newborns against infectious diseases shortly after birth. We assessed background rates of adverse pregnancy outcomes before the implementation of a maternal pertussis immunisation programme in the Netherlands, to put into perspective the safety concerns about such outcomes following immunisation.

STUDY DESIGN

In this retrospective cross-sectional study, annual numbers of pregnancy outcomes derived from the Dutch Perinatal Registry were used to calculate incidence rates per 10,000 in the 2006-2018 period. Births of ≥500 g birth weight and ≥24 + 0 w gestational age were included. Trends with moving-average-lines over the past 3 years were plotted, with 95 % confidence interval.

RESULTS

From 2006 through 2018, yearly numbers of pregnancies ranged between 158,868-175,710. Numbers of newborns ranged between 161,307-178,874, of whom 160,838-178,177 were live-born. Most outcomes were stable over time. Between 2006-2011, occurrence of labour induction increased by 68 %, and postpartum hemorrhage increased by 25 %. Both stabilised from 2011 onwards. Perinatal mortality up to day 7 or 28 postpartum decreased by 38 % and 37 %, respectively. Occurrence of low Apgar score among preterm infants born before 37 + 0 w gestational age and among term infants increased by 19 % and 27 %, respectively.

CONCLUSION

Our study on background incidences showed notable increases over time in occurrence of labour induction, postpartum hemorrhage and low Apgar score, while showing a considerable decrease in overall perinatal mortality. These findings should be considered when interpreting data on adverse events occurring since the maternal pertussis immunisation programme was implemented.

Global Perspectives on Immunization During Pregnancy and Priorities for Future Research and Development: An International Consensus Statement

Immunization during pregnancy has been recommended in an increasing number of countries. The aim of this strategy is to protect pregnant women and infants from severe infectious disease, morbidity and mortality and is currently limited to tetanus, inactivated influenza, and pertussis-containing vaccines. There have been recent advancements in the development of vaccines designed primarily for use in pregnant women (respiratory syncytial virus and group B Streptococcus vaccines). Although there is increasing evidence to support vaccination in pregnancy, important gaps in knowledge still exist and need to be addressed by future studies. This collaborative consensus paper provides a review of the current literature on immunization during pregnancy and highlights the gaps in knowledge and a consensus of priorities for future research initiatives, in order to optimize protection for both the mother and the infant.

Impact of extending the timing of maternal pertussis vaccination on hospitalized infant pertussis in England, 2014 - 2018

BACKGROUND

In October 2012 a maternal pertussis vaccination program was introduced in England for women between 28 and 32 weeks of pregnancy. In April 2016, the recommended optimal window was extended to 20-32 weeks to improve vaccine coverage and protect preterm infants.This study assesses the impact of offering maternal pertussis vaccination earlier in pregnancy on hospitalized infant pertussis cases.

METHODS

Hospitalized pertussis cases ≤60 days old in England were extracted from Hospital Episode Statistics pre-policy change and post policy change. Data were linked to laboratory-confirmed cases and clinical records were reviewed where cases were not matched. Maternal vaccine status of identified cases was established. Median hospital duration was calculated, and a competing risk survival analysis undertaken to assess multiple factors.

RESULTS

A total of 201 cases were included in the analysis. Of the 151 cases with reported gestational age, the number of hospitalizations amongst full-term infants was 60 cases pre-policy and 62 cases post policy, respectively while preterm cases declined from 20 to 9 (p=0.06). Length of hospital stay did not differ significantly after the policy change. Significantly longer hospital stays were seen in cases aged 0- 4 weeks (median of 3 more days than infants 5-8 weeks), premature infants (median of 4 more days than term infants) and cases with coinfections (median of 1 more day than those without coinfection).

CONCLUSIONS

The number of preterm infants hospitalized with pertussis in England halved after the policy change and preterm infants were no longer over-represented amongst hospitalized cases.

An Investigation of Japanese Neonatal and Maternal Antibody Status against Pertussis

To clarify the pertussis immune status of the Japanese population, we investigated levels of serum pertussis toxin (PT)-specific immunoglobulin G (IgG) antibody in infants and mothers between April 2016 and March 2018. A total of 206 infants (n = 22, < 32 weeks of gestational age [wGA]; n = 70, 32-36 wGA; n = 114, ≥ 37 wGA) and 170 mothers were enrolled. The maternal seroprevalence and antibody geometric mean titer (GMT) were 52.4% and 10.7 EU/mL, respectively. The antibody GMT, seroprevalence, and mean ratio of infant to maternal antibody titers of infants at < 32 wGA were 3.2 EU/mL, 13.6%, and 42.5%, respectively, and were significantly lower than those of infants at 32-36 wGA (9.7 EU/mL, 54.3%, and 110.2%) and infants at ≥ 37 wGA (12.1 EU/mL, 57.9%, and 112.6%). Of the 21 infants who underwent a second examination, five were positive in the first examination. Of those five, the GMT for PT had decreased by an average of 52.6% at 4.3- week intervals. In the second examination, two infants were seropositive. Approximately half of the mothers and infants were negative for anti-PT antibody. Thus, new vaccination strategies, such as the vaccination of pregnant women, are needed to prevent pertussis infection in early infancy.

Seroprevalence of Bordetella pertussis antibodies and anti-pertussis antibody response after a single dose of reduced-antigen combined diphtheria, tetanus, and acellular pertussis vaccine (Tdap) in pregnant Thai women

BACKGROUND

Maternal immunization with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) has recently been implemented to prevent infant pertussis. Tdap is still not routinely recommended in Thailand, and there are limited data to support or challenge this strategy.

OBJECTIVES

The primary aim was to determine the seroprevalence of anti-pertussis toxin antibodies (anti-PT IgG) among pregnant Thai women. The secondary aims were to evaluate antibodies response after Tdap vaccination between seronegative and seropositive mothers and to compare the different antibody titers at delivery among seropositive mothers who received Tdap to those who received tetanus-diphtheria vaccine (Td).

METHODS

This randomized clinical trial was conducted during April 2018 to April 2019 at Siriraj Hospital, Bangkok, Thailand. A total of 129 pregnant women were included. Paired blood samples for anti-PT IgG levels were obtained during the first antenatal visit and at delivery. A baseline cut-off value of <5 IU/ml indicated seronegativity. There were 29 exclusions from the original 129 enrollment. All seronegative participants (n = 69) received Tdap, while the seropositive group were randomized 1:1 to receive either Tdap (n = 18) or Td (n = 13) during 27-36 weeks' gestation. The antibody levels from both sera were compared between groups.

RESULTS

The seroprevalence of maternal anti-PT IgG was 33.3% (43/129). There was no significant difference in the increment of antibody levels after Tdap vaccination between the seronegative and seropositive groups (30.2 vs. 42 IU/ml; p = 0.183). Among seropositive groups, all Tdap recipients had increased antibody titers at delivery, while all Td recipients showed waning of immunity throughout gestation. (42 IU/ml vs. -7.4 IU/ml; p < 0.001).

CONCLUSION

Most pregnant Thai women have seronegative against pertussis. Most seropositive mothers had initial low antibody titers and their immunity significantly decreased before delivery. Our findings highlight the need for universal pertussis immunization in pregnancy regardless of individual baseline immunity.

The effectiveness of influenza vaccination in pregnancy in relation to child health outcomes: Systematic review and meta-analysis

OBJECTIVES

To determine the effectiveness of influenza vaccination during pregnancy on child health outcomes.

DESIGN

Systematic review/meta-analysis.

DATA SOURCES

Clinical Trials.gov, Cochrane Library, EMBASE, Medline, Medline in process, PubMed and Web of Science, from 1st January 1996 to 29th June 2018. An updated Medline search was performed 30th June 2018 to 31st October 2019.

METHODS

Randomised controlled trials (RCTs) and observational studies reporting health outcomes of infants and children born to women who received inactivated influenza vaccine during pregnancy. The primary outcome was infant laboratory confirmed influenza (LCI). Secondary outcomes included influenza-like illness (ILI), other respiratory illnesses, primary care, clinic visit or hospitalisations due to influenza illness and long-term respiratory childhood outcomes.

RESULTS

19 studies were included; 15 observational studies and 4 primary RCTs with an additional 3 papers reporting secondary outcomes of these RCTs. In a random effects meta-analysis of 2 RCTs including 5742 participants, maternal influenza vaccination was associated with an overall reduction of LCI in infants of 34% (95% confidence interval 15-50%). However, there was no effect of maternal influenza vaccination on ILI in infants ≤6 months old. Two RCTs were excluded from the meta-analysis for the outcome of LCI in infants (different controls used). Both of these studies showed a protective effect for infants from LCI, with a vaccine efficacy of up to 70%. Overall observational studies showed an inverse (protective) association between maternal influenza vaccination and infant LCI, hospitalisation and clinic visits due to LCI or ILI in infants and other respiratory illness in infants ≤6 months old.

CONCLUSIONS

This systematic review supports maternal influenza vaccination as a strategy to reduce LCI and influenza-related hospitalisations in young infants. Communicating these benefits to pregnant women may support their decision to accept influenza vaccination in pregnancy and increase vaccine coverage in pregnant women.

REGISTRATION

PROSPERO CRD42018102776.

Vaccination during pregnancy: current and possible future recommendations

Immunizing pregnant women to protect the mother, fetus and infant from infection has increasingly been used over the last decade. Protection against infectious diseases in neonates is mainly provided by maternal antibodies transferred from mother to infant during pregnancy through transplacental transport or after delivery via breastfeeding. Both the transplacental- and breast milk-derived maternal antibodies function as the primary source of protection against infectious diseases in neonates during the first vulnerable weeks of life. During recent infectious disease outbreaks (influenza, pertussis, Zika…) and for other infectious diseases (CMV, GBS…), pregnant women are increasingly identified as an important target for vaccination. For some of these diseases, vaccines are already on the market, and recommended during pregnancy. For others, vaccines are currently under development; furthermore, some are even specifically designed to be administered during pregnancy.Conclusion: This review article provides an overview on the rationale and main mechanism of the maternal vaccination strategy and gives a summary about the current and possible future recommendations for maternal vaccination.What is Known:• Maternal vaccination has a far-reaching potential in the protection of both women and offspring.• Currently, tetanus, pertussis and influenza vaccination during pregnancy is recommended in some countries. Several new vaccines specifically designed for use in pregnancy are currently under development.What is New:• Review providing a timely overview of the rationale and main mechanisms of the maternal vaccination strategy• Up-to-date summary of the current and possible future recommendations for maternal vaccination.

Immunological and Clinical Benefits of Maternal Immunization Against Pertussis: A Systematic Review

Infants are vulnerable to pertussis infection particularly before initiation of pertussis vaccination. Maternal pertussis vaccination during pregnancy has been introduced in a number of countries in order to confer on young infants indirect protection from the disease through transplacental transfer of maternal antibodies. We reviewed the evidence on the immunogenicity and efficacy of maternal pertussis vaccination during pregnancy. A systematic search of PubMed/MEDLINE, EMBASE, Scopus, Cochrane Database of Systematic Reviews, ProQuest, and Science Direct was undertaken to identify studies published between January 1995 and December 2018. This review was not specific to any particular pertussis vaccine but included applicable data on available pertussis vaccines administered to pregnant women. The search identified 40 publications for inclusion in this review. Vaccination during pregnancy elicited robust maternal immune responses against all vaccine antigens and resulted in high placental transfer of pertussis antibodies to the infant that persisted well beyond delivery. Vaccination during the second or early third trimesters was considered ideal for antibody quantity and functionality. Although blunting of immune responses to some antigens in the primary immunization series was documented in neonates born to women vaccinated during pregnancy, there was no apparent adverse effect on vaccine efficacy. Multiple studies conducted in diverse settings have confirmed the effectiveness of maternal pertussis vaccination during pregnancy in preventing pertussis in infants prior to receipt of their first primary vaccine dose and beyond. These findings collectively underscore the value of maternal pertussis vaccination during pregnancy in protecting vulnerable infants too young to be vaccinated.Funding Sanofi Pasteur.Plain Language Summary Plain language summary available for this article.

Missed vaccinations and critical care admission: all you may wish to know or rediscover-a narrative review

Most vaccines are so effective that they could lead to the control/elimination of the diseases they target and directly impact on intensive care admissions or complications. This is best illustrated by the use of vaccines against Haemophilus influenzae type b, Streptococcus pneumoniae, zoster, yellow fever, Ebola virus, influenza or measles-but also by third party strategies such as maternal, toddler and care-giver immunization. However, each of these vaccine-induced protection is threatened by insufficient vaccine uptake. Here, we briefly discuss how vaccine hesitancy has led to the resurgence of diseases that were considered as controlled and explore the effect of vaccine-hesitant healthcare workers on nosocomial infections. As intensive care physicians are in charge of polymorbid patients, we briefly summarize the current recommendations for vaccinations in high-risk patients. We finally give some perspective on ongoing research, and discuss how institutional policies and intensive care physicians could play a role in increasing the impact of vaccination, overall and in intensive care units.

The effect of maternal antibodies on the cellular immune response after infant vaccination: A review

During the last few decades, maternal immunization as a strategy to protect young infants from infectious diseases has been increasingly recommended, yet some issues have emerged. Studies have shown that for several vaccines, such as live attenuated, toxoid and conjugated vaccines, high maternal antibody titers inhibit the infant's humoral immune response after infant vaccination. However, it is not clear whether this decreased antibody titer has any clinical impact on the infant's protection, as the cellular immune responses are often equally important in providing disease protection and may therefore compensate for diminished antibody levels. Reports describing the effect of maternal antibodies on the cellular immune response after infant vaccination are scarce, probably because such studies are expensive, labor intensive and utilize poorly standardized laboratory techniques. Therefore, this review aims to shed light on what is currently known about the cellular immune responses after infant vaccination in the presence of high (maternal) antibody titers both in animal and human studies. Overall, the findings suggest that maternally derived antibodies do not interfere with the cellular immune responses after infant vaccination. However, more research in humans is clearly needed, as most data originate from animal studies.

Immunogenicity and Efficacy Evaluation of Subunit Astrovirus Vaccines

A full understanding of the immune response to astrovirus (AstV) infection is required to treat and control AstV-induced gastroenteritis. Relative contributions of each arm of the immune system in restricting AstV infection remain unknown. In this study, two novel subunit AstV vaccines derived from capsid protein (CP) of mink AstV (MAstV) such as CPΔN (spanning amino acids 161–775) and CPΔC (spanning amino acids 1–621) were evaluated. Their immunogenicity and cytokine production in mice, as well as protective efficacy in mink litters via maternal immunization, were studied. Truncated CPs induced higher levels of serum anti-CP antibodies than CP, with the highest level for CPΔN. No seronegativity was detected after booster immunization with either AstV CP truncates in both mice and mink. All mink moms stayed seropositive during the entire 104-day study. Furthermore, lymphoproliferation responses and Th1/Th2 cytokine induction of mice splenocytes ex vivo re-stimulated by truncated CPs were significantly higher than those by CP, with the highest level for CPΔN. Immunization of mink moms with truncated CPs could suppress virus shedding and clinical signs in their litters during a 51-day study after challenge with a heterogeneous MAstV strain. Collectively, AstV truncated CPs exhibit better parameters for protection than full-length CP.

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

INTRODUCTION

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

ETHICS AND DISSEMINATION

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

Antibody responses to Bordetella pertussis and other childhood vaccines in infants born to mothers who received pertussis vaccine in pregnancy - a prospective, observational cohort study from the United Kingdom

The maternal Tdap (tetanus, diphtheria and acellular pertussis) vaccination programme in the United Kingdom has successfully reduced cases of pertussis in young infants. In addition to prevention of pertussis cases, it is also important to investigate the persistence of maternal antibodies during infancy and the possible interference of maternal antibodies with infant responses to vaccines. We recruited mother–infant pairs from vaccinated and unvaccinated pregnancies and measured concentrations of immunoglobulin (Ig)G against pertussis toxin (PTx), filamentous haemagglutinin (FHA), pertactin (Prn), diphtheria toxin (DTx), tetanus toxoid (TTx) Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae in mothers and infants at birth, and in infants at 7 weeks and at 5 months. Thirty‐one mother–infant pairs were tested. Tdap‐vaccinated women had significantly higher antibody against Tdap antigens, compared to unvaccinated women (DTx, P = 0·01; PTx, FHA, Prn and TTx, P < 0·001). All antibodies were actively transferred to the infants (transfer ratio  > 1) with higher transfer of DTx (P = 0·04) and TTx (P = 0·02) antibody in Tdap‐vaccinated pregnancies compared to unvaccinated pregnancies. Infants from Tdap‐vaccinated pregnancies had significantly elevated antibodies to all antigens at birth (P < 0.001) and at 7 weeks (FHA, Prn, TTx, P < 0·001; DTx, P = 0.01; PTx, P = 0·004) compared to infants from unvaccinated pregnancies. Infants from Tdap‐vaccinated and ‐unvaccinated pregnancies had comparable antibody concentrations following primary pertussis immunization (PTx, P = 0·77; FHA, P = 0·58; Prn, P = 0·60; DTx, P = 0·09; TTx, P = 0·88). These results support maternal immunization as a method of protecting vulnerable infants during their first weeks of life.

Neonatal Immunity to Bordetella pertussis Infection and Current Prevention Strategies

Bordetella pertussis is the bacterial agent of whooping cough, an infectious disease that is reemerging despite high vaccine coverage. Newborn children are the most affected, not only because they are too young to be vaccinated but also due to qualitative and quantitative differences in their immune system, which makes them more susceptible to infection and severe manifestations, leading to a higher mortality rate comparing to other groups. Until recently, prevention consisted of vaccinating children in the first year of life and the herd vaccination of people directly in touch with them, but the increase in cases demands more effective strategies that can overcome the developing immune response in early life and induce protection while children are most vulnerable.

Pertussis: New preventive strategies for an old disease

In the last twenty years, despite high vaccination coverage, epidemics of pertussis are occurring in both developing and developed countries. Many reasons could explain the pertussis resurgence: the increasing awareness of the disease, the availability of new diagnostic tests with higher sensitivity, the emergence of new Bordetella pertussis (B. pertussis) strains different from those contained in the current vaccines, the asymptomatic transmission of B. pertussis in adolescents and adults and the shorter duration of protection given by the acellular pertussis (aP) vaccine. New preventive strategies have already been implemented, such as booster doses of aP vaccine in adolescents and adults, maternal immunisation during pregnancy and the "cocooning" strategy, but more are still needed. Knowing what is new about this old disease is necessary to reduce its incidence and to protect infants too young to be vaccinated, which have the highest risk of complications and death.

The impact of timing of maternal influenza immunization on infant antibody levels at birth

Pregnant women and infants are at an increased risk of severe disease after influenza infection. Maternal immunization is a potent tool to protect both these at-risk groups. While the primary aim of maternal influenza vaccination is to protect the mother, a secondary benefit is the transfer of protective antibodies to the infant. A recent study using the tetanus, diphtheria and acellular pertussis (Tdap) vaccine indicated that children born to mothers immunized in the second trimester of pregnancy had the highest antibody titres compared to children immunized in the third trimester. The aim of the current study was to investigate how the timing of maternal influenza immunization impacts infant antibody levels at birth. Antibody titres were assessed in maternal and cord blood samples by both immunoglobulin (Ig)G-binding enzyme-linked immunosorbent assay (ELISA) and haemagglutination inhibition assay (HAI). Antibody titres to the H1N1 component were significantly higher in infants born to mothers vaccinated in either the second or third trimesters than infants born to unvaccinated mothers. HAI levels in the infant were significantly lower when maternal immunization was performed less than 4 weeks before birth. These studies confirm that immunization during pregnancy increases the antibody titre in infants. Importantly, antibody levels in cord blood were significantly higher when the mother was vaccinated in either trimesters 2 or 3, although titres were significantly lower if the mother was immunized less than 4 weeks before birth. Based on these data, seasonal influenza vaccination should continue to be given in pregnancy as soon as it becomes available.

The Fourth International Neonatal and Maternal Immunization Symposium (INMIS 2017): Toward Integrating Maternal and Infant Immunization Programs

This report provides an overview of the proceedings of the 4th International Maternal and Neonatal Immunization Symposium, where presentations focused on the state-of-the-art research on the development and implementation of vaccines given during pregnancy for the protection of mothers and infants.

Prevention of serious infections in pregnant mothers, newborns, and young infants through immunization during pregnancy and in early life has the potential to further reduce maternal and neonatal morbidity and mortality worldwide. In the past decade, research in this field has advanced substantially, from the understanding of the biology and immunology of pregnancy and early life, to the active development of several candidate vaccines, for which challenges and opportunities for global implementation are under consideration. Experts from academia, industry, regulatory and funding agencies, public health, and international organizations met in Brussels (Belgium) from 10 to 12 September 2017, at the 4th International Neonatal and Maternal Immunization Symposium (INMIS), to review the most relevant advances in maternal and neonatal immunization. The overarching focus of the conference was to identify the path forward to achieve integration of maternal and early life immunization strategies for the successful implementation of vaccines in antenatal care and pediatric programs for reduction of maternal and infant mortality worldwide.

IMPORTANCE This report provides an overview of the proceedings of the 4th International Maternal and Neonatal Immunization Symposium, where presentations focused on the state-of-the-art research on the development and implementation of vaccines given during pregnancy for the protection of mothers and infants.

Immunogenicity and Safety of Monovalent Acellular Pertussis Vaccine at Birth: A Randomized Clinical Trial

IMPORTANCE

An alternative option to maternal vaccination to prevent severe pertussis in infants is vaccination at birth. Data are needed on the immunogenicity and safety of a birth dose of monovalent acellular pertussis (aP) vaccine.

OBJECTIVE

To compare IgG antibody responses to vaccine antigens at 6, 10, 24, and 32 weeks of age between newborn infants receiving the aP vaccine and hepatitis B vaccine (HBV) or HBV alone.

DESIGN, SETTING, AND PARTICIPANTS

A randomized clinical trial was conducted at 4 sites in Australia (Sydney, Melbourne, Adelaide, and Perth) between June 11, 2010, and March 14, 2013, among 440 healthy term (>36 weeks' gestation) infants aged less than 5 days at recruitment. Statistical analysis was performed from March 1, 2015, to June 2, 2016.

INTERVENTION

Newborns received HBV and, after stratification by maternal receipt of adult-formulated aP-containing vaccine (tetanus toxoid, reduced diphtheria toxoid, and pertussis antigen content [Tdap]) prior to pregnancy, were block randomized to receive the aP vaccine (without diphtheria or tetanus) within 5 days of birth or not. At 6, 16, and 24 weeks, infants received a hexavalent vaccine with pediatric-formulated diphtheria, tetanus and pertussis antigens (DTaP), Haemophilus influenzae type b (Hib), HBV, and polio vaccine, as well as the 10-valent pneumococcal conjugate vaccine.

MAIN OUTCOMES AND MEASURES

Detectable (>5 enzyme-linked immunosorbent assay units per milliliter) and geometric mean concentrations of IgG antibody to pertussis toxin (PT), pertactin, and filamentous hemagglutinin at 6, 10, and 24 weeks stratified by maternal Tdap history, and antibody at 32 weeks to HBV, Hib, polio, diphtheria, tetanus, and pneumococcal serotypes. The primary outcome was detectable IgG to both PT and pertactin at 10 weeks.

RESULTS

A total of 440 infants (207 girls and 233 boys; median gestation, 39.2 weeks) were randomized to receive the aP vaccine plus HBV (n = 221) or HBV only (control group; n = 219). At 10 weeks, 192 of 206 infants who received the aP vaccine (93.2%) had detectable antibodies to both PT and pertactin vs 98 of 193 infants in the control group (50.8%) (P < .001), with the geometric mean concentration for PT IgG 4-fold higher among the group that received the aP vaccine. At age 32 weeks, all infants (n = 181 with sera available for testing) who received the aP vaccine at birth had detectable PT IgG and significantly lower IgG geometric mean concentrations for Hib, hepatitis B, diphtheria, and tetanus antibodies. Local and systemic adverse events were similar between both groups at all time points.

CONCLUSIONS AND RELEVANCE

The monovalent aP vaccine is immunogenic and safe in neonates and, if licensed and available, would be valuable for newborns whose mothers did not receive the Tdap vaccine during pregnancy.

TRIAL REGISTRATION

http://anzctr.org.au Identifier: ACTRN12609000905268.

Current antenatal pertussis vaccination guidelines miss preterm infants: An epidemiological study from the Northern Territory

IMPORTANCE

Assessing gaps in antenatal pertussis vaccination to increase coverage.

INTRODUCTION

Antenatal pertussis vaccination has been proven effective in reducing pertussis disease in infants. Current guidelines recommend maternal pertussis vaccination from 28 weeks gestation. The aim of this study is to determine antenatal pertussis vaccination coverage in the Northern Territory and potential socio-demographic factors affecting uptake, using validated birth and immunisation data.

METHODS

Cross-sectional population study including all viable births (from 24 weeks gestation) in Northern Territory public hospitals in 2016.

RESULTS

There were 3392 viable delivery episodes in 2016 with 48.9% coverage against maternal pertussis based on current guidelines. Mothers <35 years old were more likely to receive antenatal vaccination (adjusted odds ratio (aOR) = 1.26, CI 1.035-1.52, P = 0.021). Pertussis vaccination coverage for preterm births was low at 0% for extreme, 18.86% for very preterm and 39.8% for moderate preterm births, with an overall coverage of 33.5% for all preterm births. Term births were two times more likely than preterm births to have had mothers receive an antenatal diphtheria toxoid, tetanus toxoid and acellular pertussis vaccine (aOR = 1.957, CI 1.53-2.50, P < 0.001).

CONCLUSIONS

A significant proportion (66.5%) of preterm babies are not benefiting from protection against pertussis with the current pertussis vaccination policy from 28 weeks gestation. As timing of birth cannot be predetermined, a review of safety and acceptability of pertussis vaccine administration in the second trimester is needed. Implementation of pertussis vaccination from 20 weeks gestation will provide a wider vaccination period and maximise the protection of all infants including pre-term infants from pertussis.