A phase IV, multi-centre, randomized clinical trial comparing two pertussis-containing vaccines in pregnant women in England and vaccine responses in their infants

Vaccination during pregnancy and modulation of IgG response to pertussis vaccines in infants: The impact of different vaccine formulations

The IgG response following infant diphtheria-tetanus-acellular pertussis (DTaP) immunization is influenced by the formulation of the infant and/or the adult vaccine (Tdap) given during pregnancy. DTaP vaccines containing either 3 (DTaP3) or 5 (DTaP5) pertussis antigens are commonly used. By conducting a secondary analysis of a large randomized controlled trial, we compared IgG levels against pertussis vaccine antigens in children of Td- and Tdap5-vaccinated mothers, after stratifying by infant vaccine formulation. After immunization with a primary series of DTaP5, but not DTaP3, IgG GMCs against pertussis antigens were significantly lower in infants of Tdap-immunized mothers compared with infants of Td-vaccinated mothers (pertussis toxin: GMC = 52.3[Tdap5] vs 83.5[Td], p < 0.001). Before and after the DTaP booster dose, IgG GMCs were similar in infants of Tdap- and Td-immunized mothers specifically when infants received the DTaP3 vaccine. The combination of the TdaP5 vaccine for mothers and the DTaP3 vaccine for children could attenuate Tdap-associated immunomodulation.

Maternal pertussis immunization and the blunting of routine vaccine effectiveness: a meta-analysis and modeling study

A key goal of pertussis control is to protect infants too young to be vaccinated, the age group most vulnerable to this highly contagious respiratory infection. In the last decade, maternal immunization has been deployed in many countries, successfully reducing pertussis in this age group. Because of immunological blunting, however, this strategy may erode the effectiveness of primary vaccination at later ages. Here, we systematically reviewed the literature on the relative risk (RR) of pertussis after primary immunization of infants born to vaccinated vs. unvaccinated mothers. The four studies identified had ≤6 years of follow-up and large statistical uncertainty (meta-analysis weighted mean RR: 0.71, 95% CI: 0.38-1.32). To interpret this evidence, we designed a new mathematical model with explicit blunting mechanisms and evaluated maternal immunization's short- and long-term impact on pertussis transmission dynamics. We show that transient dynamics can mask blunting for at least a decade after rolling out maternal immunization. Hence, the current epidemiological evidence may be insufficient to rule out modest reductions in the effectiveness of primary vaccination. Irrespective of this potential collateral cost, we predict that maternal immunization will remain effective at protecting unvaccinated newborns, supporting current public health recommendations.

Maternal Pertussis Vaccination, Infant Immunization, and Risk of Pertussis

OBJECTIVES

Following the introduction of jurisdictional maternal pertussis vaccination programs in Australia, we estimated maternal vaccine effectiveness (VE) and whether maternal pertussis vaccination modified the effectiveness of the first 3 primary doses of pertussis-containing vaccines.

METHODS

We conducted a population-based cohort study of 279 418 mother-infant pairs using probabilistic linkage of administrative health records in 3 Australian jurisdictions. Infants were maternally vaccinated if their mother had a documented pertussis vaccination ≥14 days before birth. Jurisdictional immunization records were used to identify receipt of the first 3 infant doses of pertussis-containing vaccines. Infant pertussis infections were identified using notifiable disease records. VE was estimated using Cox proportional hazard models.

RESULTS

Pertussis was administered during 51.7% (n = 144 429/279 418) of pregnancies, predominantly at 28-31 weeks' gestation. VE of maternal pertussis vaccination declined from 70.4% (95% confidence interval [CI], 50.5-82.3) among infants <2 months old to 43.3% (95% CI, 6.8-65.6) among infants 7-8 months old and was not significant after 8 months of age. Although we observed slightly lower VE point estimates for the third dose of infant pertussis vaccine among maternally vaccinated compared with unvaccinated infants (76.5% vs 92.9%, P = .002), we did not observe higher rates of pertussis infection (hazard ratio, 0.70; 95% CI, 0.61-3.39).

CONCLUSIONS

Pertussis vaccination near 28 weeks' gestation was associated with lower risk of infection among infants through 8 months of age. Although there was some evidence of lower effectiveness of infant vaccination among maternally vaccinated infants, this did not appear to translate to greater risk of disease.

Safety and Clinical Benefits of Adacel® and Adacel®-Polio Vaccination in Pregnancy: A Structured Literature Review

Vaccination in pregnancy using a tetanus toxoid, reduced dose diphtheria toxoid, and reduced dose acellular pertussis (Tdap) vaccine is important for prevention of severe pertussis disease in young infants. The objectives of this systematic literature review were to search for original research studies evaluating the vaccine effectiveness, immunogenicity, and safety of Adacel®/Adacel-Polio® used during pregnancy to prevent pertussis disease in young infants. Medical databases used included EMBASE, BIOSIS Previews, and Chemical Abstracts, with search terms related to pregnancy, vaccines/immunization, safety, pertussis, effectiveness/efficacy, and immune response; other potentially eligible reports were included where applicable. Search results were restricted to literature published from 1 January 1995 to 26 July 2021. A total of 2021 articles and 4 other reports were identified for primary review. A total of 49 publications qualified for inclusion after primary and secondary reviews. Effectiveness studies of Adacel or Adacel-Polio given in pregnancy consistently showed high levels of protection from pertussis disease in the newborn (vaccine effectiveness: 91-93%). In immunogenicity studies, the response in pregnant women was consistent with that of non-pregnant women. Infants of mothers vaccinated with Adacel or Adacel-Polio in pregnancy had higher anti-pertussis antibody levels at birth and at 2 months of age compared to infants born to women vaccinated with comparator vaccines, placebo, or those not vaccinated during pregnancy. There was evidence of a slightly decreased response to primary pertussis vaccination in infants of mothers vaccinated with Adacel or Adacel-Polio, but this was not thought to be clinically significant. In safety studies, Adacel or Adacel-Polio vaccination was well tolerated by pregnant woman and not associated with pregnancy, postpartum, or neonatal complications. In conclusion, Adacel or Adacel-Polio vaccination in pregnancy is highly effective in protecting young infants from pertussis disease, with a favorable safety profile for both pregnant women and their infants.

Next-Generation TB Vaccines: Progress, Challenges, and Prospects

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is a prevalent global infectious disease and a leading cause of mortality worldwide. Currently, the only available vaccine for TB prevention is Bacillus Calmette-Guérin (BCG). However, BCG demonstrates limited efficacy, particularly in adults. Efforts to develop effective TB vaccines have been ongoing for nearly a century. In this review, we have examined the current obstacles in TB vaccine research and emphasized the significance of understanding the interaction mechanism between MTB and hosts in order to provide new avenues for research and establish a solid foundation for the development of novel vaccines. We have also assessed various TB vaccine candidates, including inactivated vaccines, attenuated live vaccines, subunit vaccines, viral vector vaccines, DNA vaccines, and the emerging mRNA vaccines as well as virus-like particle (VLP)-based vaccines, which are currently in preclinical stages or clinical trials. Furthermore, we have discussed the challenges and opportunities associated with developing different types of TB vaccines and outlined future directions for TB vaccine research, aiming to expedite the development of effective vaccines. This comprehensive review offers a summary of the progress made in the field of novel TB vaccines.

Optimising the timing of whooping cough immunisation in mums (OpTIMUM) through investigating pertussis vaccination in pregnancy: an open-label, equivalence, randomised controlled trial

BACKGROUND

Pertussis vaccination in pregnancy is recommended in many countries to provide protection to young infants. The best timing for this vaccination is uncertain. In the UK, vaccination is recommended between 16 weeks and 32 weeks of gestation. In this trial we aimed to investigate the equivalence of three time periods for pertussis vaccination in pregnancy.

METHODS

In this open-label, equivalence, randomised controlled trial to investigate equivalence of different time windows for pertussis vaccination in pregnancy, participants were randomly assigned (1:1:1 ratio) to receive a pertussis-containing vaccine (Boostrix-inactivated poliovirus vaccine) in one of three gestational age groups, comprising group 1 (≤23 weeks + 6 days), group 2 (24-27 weeks + 6 days), and group 3 (28-31 weeks + 6 days) using a computer-generated randomisation list. The primary outcome was concentration of pertussis-specific antibodies in the infant born at term at birth. Maternal blood sampling was done before and 2 weeks after vaccination and at delivery, together with a cord sample, and an infant sample was collected at least 4 weeks after primary vaccination. Reactogenicity was assessed for 7 days after vaccination. This trial was registered with ClinicalTrials.gov (NCT03908164).

FINDINGS

Between May 7, 2019, and Feb 13, 2020, of 1010 women assessed for eligibility, 364 women were recruited and 351 received the intervention (120 in group 1, 119 in group 2, and 112 in group 3). Equivalence of time periods was demonstrated for anti-pertussis toxin and anti-pertactin IgG concentrations. The cord blood geometric mean concentrations of anti-filamentous haemagglutinin IgG were higher with increasing gestational age at vaccination, such that for infants in group 1 (≤23 weeks + 6 days), equivalence to group 3 (28-31 weeks + 6 days) was not shown. Reported rates of fever were similar between study groups.

INTERPRETATION

Pertussis vaccination at three different time intervals in pregnancy resulted in equivalent concentrations of IgG antibodies in infants against two of the three pertussis antigens assessed. Overall, these findings support recommendations to vaccinate any time between 16 weeks and 32 weeks of gestation.

FUNDING

The Thrasher Research Fund and the National Immunisation Schedule Evaluation Consortium through the National Institute for Health and Care Research policy research programme.

Effect of maternal immunisation with multivalent vaccines containing inactivated poliovirus vaccine (IPV) on infant IPV immune response: A phase 4, multi-centre randomised trial

Multivalent diphtheria, tetanus, acellular pertussis and inactivated poliovirus vaccine (DTaP/IPV) has been offered to pregnant women in the United Kingdom since 2012. To assess the impact of maternal DTaP/IPV immunisation on the infant immune response to IPV, we measured poliovirus-specific neutralising antibodies at 2, 5 and 13 months of age in a randomised, phase 4 study of Repevax or Boostrix/IPV in pregnancy and in a non-randomised group born to women not given DTaP/IPV in pregnancy. Infants whose mothers received DTaP/IPV were less likely to seroconvert after three IPV doses than those whose mothers did not receive DTaP/IPV. At 13 months of age, 63/110 (57.2 %), 46/108 (42.6 %) and 40/108 (37.0 %) were seropositive to types 1 to 3, compared with 20/22 (90.9 %), 20/22 (90.9 %) and 14/20 (70.0 %) (p-values 0.003, <0.001 and 0.012). UK infants whose mothers are given DTaP/IPV in pregnancy may be insufficiently protected against poliomyelitis until their pre-school booster.

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.

Diphtheria, tetanus, and pertussis immunity among healthcare professionals and pregnant women in the Moscow region, Russian federation: A preliminary cross-sectional study

Despite more than 50 years of primary immunization against diphtheria, pertussis, and tetanus in Russia, complicated illnesses, including fatal ones, still occur. The goal of this preliminary cross-sectional study is to see how well pregnant women and healthcare workers are protected against diphtheria, pertussis, and tetanus. The required sample size (pregnant women and healthcare professionals, as well as pregnant women of two age categories) for this preliminary cross-sectional study was calculated using a confidence value of 0.95 and a probability of 0.05. The required number of participants in each group calculated sample size must be at least 59 people. In the Moscow region (Solnechnogorsk city, Russia), a cross-sectional study of pregnant patients and healthcare professionals interacting with children regularly as part of their job from numerous medical organizations was conducted in the year 2021 (n = 655). Antibodies to diphtheria, tetanus, and pertussis toxoids and microorganisms were measured using an enzyme-linked immunosorbent assay (ELISA). The STATISTICA and IBM SPSS Statistics 26.0 were used to process the study results statistically. Descriptive statistics methods, the Mann-Whitney U-test, discriminant analysis with the stepwise selection and analysis of ROC-curves were applied. IgG against diphtheria was found in 99.5% of pregnant women, tetanus in 91.5%, and pertussis in only 36.5%. According to the results of the discriminant analysis, the value of IgG to pertussis is linked to the value of IgA to pertussis and the gestational periods. Immunity to diphtheria was discovered in 99.1% of medical personnel, tetanus in 96.9%, and pertussis in 43.9%, no significant variations with age. When comparing the levels of immunity of pregnant women and healthcare professionals, it was shown that healthcare workers have greater levels of immunity against diphtheria and tetanus. The novel contribution of this study is that it will reveal the proportion of those vulnerable to pertussis, diphtheria, and tetanus among health workers and pregnant women in all age groups under the current national immunization program in Russia. Considering the data obtained from the preliminary cross-sectional study, we believe that it is necessary to conduct a full-scale study on a larger sample and, based on that, make certain changes to the national immunization program in Russia.

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.

An observational, cohort, multi-centre, open label phase IV extension study comparing preschool DTAP-IPV booster vaccine responses in children whose mothers were randomised to one of two pertussis-containing vaccines or received no pertussis-containing vaccine in pregnancy in England

An antenatal pertussis vaccination programme was introduced in 2012 in the UK in the context of a national outbreak of pertussis. It has been shown that a lower antibody response to primary immunisation can be seen for certain pertussis antigens in infants born to women who received pertussis-containing antenatal vaccines, a phenomenon known as blunting. The longer-term impact of this has not been documented previously, and accordingly was evaluated in this study. Children were predominantly recruited from a previous study in which their mothers had received acellular pertussis-containing antenatal vaccines (dTaP₃-IPV [diphtheria toxoid, tetanus toxoid, three antigen acellular pertussis and inactivated polio] or dTaP₅-IPV [diphtheria toxoid, tetanus toxoid, five antigen acellular pertussis and inactivated polio]), or no pertussis-containing vaccine. Blood samples were obtained prior to and one month after the acellular pertussis-containing preschool booster (dTaP₅-IPV) was given at around age 3 years 4 months. Pre- and post-booster immunoglobulin G (IgG) geometric mean concentrations (GMCs) against pertussis toxin, filamentous haemagglutinin, fimbriae 2 & 3, and pertactin, were compared. Prior to the receipt of the preschool booster, there was no difference in the IgG GMCs against pertussis-specific antigens between children born to women vaccinated with dTaP₃-IPV and dTaP₅-IPV; however, IgG GMCs against pertussis toxin were significantly lower in children born to women vaccinated with dTaP₃-IPV compared with children born to unvaccinated women (geometric mean ratio 0.42 [95 % CI 0.22-0.78], p = 0.03). One month after the receipt of the preschool booster there was no differences between the groups. The blunting effect of antenatal pertussis vaccine on pertussis responses in children can persist until preschool age, although it is overcome by the administration of a booster dose. ClinicalTrials.gov registration number: NCT03578120.

Effectiveness of maternal pertussis vaccination in Singapore: A test-negative case-control study

Pertussis vaccination (Tdap -Tetanus-diphtheria-acellular pertussis) for pregnant women has been recommended since November 2017 in Singapore. In this prospective test-negative case-control study from 2018 to 2019, we aimed to evaluate vaccine effectiveness (VE) against pertussis infection and pertussis-related intensive care unit (ICU) admission according to Tdap (Tetanus-diphtheria-acellular pertussis) during pregnancy and/or infant pertussis vaccination. A total of 58 children (26 cases, 32 controls) were recruited with 4 ICU admissions. The median age was 3 months (interquartile range [IQR] 1.50-4.56 months). Overall, 25.9 % of mothers had received antenatal Tdap vaccination and 43.1 % of infants received pertussis vaccination, majority only 1 dose. Tdap in pregnancy alone without infant vaccine or with 0-1 infant dose had a VE of 97.62 % (95 % confidence interval [CI] 53.25-99.88 %), 98.17 % (95 %CI 66.61-99.9 %) respectively, against pertussis infection and 71.9 % (95 %CI 0.0-98.64), 75.86 % (95 % CI 0.0-98.78) respectively, against ICU admissions. Conclusion: Maternal Tdap vaccination was highly protective against infant pertussis and should be routinely recommended for all pregnant women.

The half-life of maternal transplacental antibodies against diphtheria, tetanus, and pertussis in infants: an individual participant data meta-analysis

AIM

There are few reliable estimates of the half-lives of maternal antibodies to the antigens found in the primary series vaccines. We aimed to calculate the half-lives of passively acquired diphtheria, tetanus and pertussis (DTP) antibodies in infants. We aimed to determine whether decay rates varied according to country, maternal age, gestational age, birthweight, World Bank income classifications, or vaccine received by the mother during pregnancy.

METHODS

De-identified data from infants born to women taking part in 10 studies, in 9 countries (UK, Belgium, Thailand, Vietnam, Canada, Pakistan, USA, Guatemala and the Netherlands) were combined in an individual participant data meta-analysis. Blood samples were taken at two timepoints before any DTP-containing vaccines were received by the infant: at birth and at 2-months of age. Decay rates for each antigen were log₂-transformed and a mixed effects model was applied. Half-lives were calculated by taking the reciprocal of the absolute value of the mean decay rates.

RESULTS

Data from 1426 mother-infant pairs were included in the analysis. The half-lives of the 6 antigen-specific maternal antibodies of interest were similar, with point estimates ranging from 28.7 (95% CI: 24.4 - 35) days for tetanus toxoid antibodies to 35.1 (95% CI: 30.7 - 41.1) days for pertactin antibodies. The decay of maternal antibodies did not significantly differ by maternal age, gestational age, birthweight, maternal vaccination status or type of vaccine administered.

CONCLUSION

Maternal antibodies decay at different rates for the different antigens; however, the magnitude of the difference is small. Decay rates are not modified by key demographic or vaccine characteristics.