Associations Between Maternal Immunisation and Reduced Rates of Preterm Birth and Stillbirth: A Population Based Retrospective Cohort Study

Safety of pertussis vaccination in pregnancy and effectiveness in infants: a Danish national cohort study 2019-2023

OBJECTIVES

Recent surges in pertussis spread have renewed focus on pertussis vaccination strategies. Denmark implemented pertussis vaccination during pregnancy in 2019 to protect infants under 3 months. This nationwide study assessed the real-world safety and effectiveness of acellular pertussis vaccination during pregnancy.

METHODS

Using nationwide Danish registers, we included all pregnancies beyond 24 gestational weeks and all liveborn children from November 1, 2019, to June 1, 2023, with follow-up until December 31, 2023. Maternal safety outcomes included hypertension, preeclampsia, chorioamnionitis, preterm birth, and stillbirth. Infant safety outcomes included neonatal mortality, neonatal intensive care unit admission, and sepsis. Vaccine effectiveness was evaluated against laboratory-confirmed pertussis and related hospital contacts. For maternal safety, vaccinated individuals were matched 1:1 to unvaccinated individuals based on gestational days, calendar week, and region. Infant outcomes were assessed among the cohort of all liveborn children with follow-up until 3 months of age. Analyses were adjusted for a range of demographic, socioeconomic and medical characteristics.

RESULTS

Among 50 851 vaccinated and 50 851 unvaccinated individuals during pregnancy, initial analyses showed an increased risk of hypertension and preeclampsia after pertussis vaccination. However, after adjusting for influenza and COVID-19 vaccination during pregnancy, pertussis vaccination was not associated with increased risks of any maternal safety outcomes including hypertension (incidence rate ratio 0.98, 0.94-1.02), mild preeclampsia (0.97, 0.92-1.02), and severe preeclampsia or haemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome (0.95, 0.86-1.05). Among 215 974 liveborn children, 108 350 were exposed to the vaccine. Vaccination was not associated with adverse infant outcomes and yielded a 72% (42-87%) effectiveness against laboratory-confirmed pertussis (9 vs. 32 events).

DISCUSSION

Pertussis vaccination in pregnancy was effective in preventing infant pertussis and was not associated with adverse pregnancy or infant outcomes. Future studies should, however, examine whether other vaccines or the administration of multiple vaccines during pregnancy pose an increased maternal risk of hypertensive disorders in pregnancy.

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

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

Factors Associated with Early Versus Late Uptake of the COVID-19 Vaccine during Pregnancy over Time in Australia: A Population-Based Cohort Study

BACKGROUND

Pregnant women are at an increased risk of hospitalisation, admission to the intensive care unit, mechanical ventilation, and death from SARS-CoV-2 infection. The aim of this study is to determine the predictive factors associated with COVID-19 vaccine uptake during pregnancy over time in a population with a high background uptake of maternal influenza and pertussis vaccination.

METHODS

This is a population-based, cohort study of all pregnant women who gave birth in Victoria, Australia between 1 July 2021 and 30 June 2022. Data from the Victorian Perinatal Data Collection were analysed using univariable and multivariable logistic regression.

RESULTS

This study reports on 77,719 women who gave birth over a 12 month period, of whom 49,281 (63.4%) received a COVID-19 vaccine, 54,887 (70.6%) received an influenza vaccination and 63,594 (81.8%) received a pertussis vaccine by the time of delivery. Pregnant women aged >30 years (aOR 1.31 CI 1.27, 1.36), who had >=8 antenatal visits (aOR 1.08 CI 1.04, 1.12), and those who received influenza vaccine (aOR 1.23 CI 1.19, 1.28) were more likely to have received a COVID-19 vaccine. Those who smoked (aOR 0.7 CI 0.66, 0.74), were First Nations (aOR 0.83 CI 0.74, 0.93) and those who gave birth in public hospitals (aOR 0.65 CI 0.63, 0.68) were less likely to receive COVID-19 vaccine in the first 12 months of the rollout.

CONCLUSION

Maternal age, smoking, parity and Indigenous status were factors associated with delayed and sustained lower coverage, even in a population with background maternal influenza and pertussis coverage of 70.6% and 81.8%, respectively.

Effect of telehealth-integrated antenatal care on pregnancy outcomes in Australia: an interrupted time-series analysis

BACKGROUND

During the COVID-19 pandemic, rapid integration of telehealth into antenatal care occurred to support ongoing maternity care. A programme of this scale had not been previously implemented. We evaluated whether telehealth-integrated antenatal care in an Australian public health system could achieve pregnancy outcomes comparable to those of conventional care to assess its safety and efficacy.

METHODS

Routinely collected data for individuals who gave birth at Monash Health (Melbourne, VIC, Australia) during a conventional care period (Jan 1, 2018, to March 22, 2020) and telehealth-integrated period (April 20, 2020, to April 25, 2021) were analysed. We included all births that occurred at 20 weeks' gestation or later or with a birthweight of at least 400 g (if duration of gestation was unknown). We excluded multiple births, births for which private antenatal care was received, and births to individuals transferred from other hospitals or who had no antenatal care. Baseline demographics, telehealth uptake, and pregnancy complications (related to pre-eclampsia, fetal growth restriction [FGR], gestational diabetes, stillbirth, neonatal intensive care [NICU] admission, and preterm birth [<37 weeks' gestation]) were compared using comparative statistics and an interrupted time-series analysis. Results were stratified by care stream, with high-risk models consisting of obstetric specialist-led care, and all other streams categorised as low-risk models. The impact of the integrated period on outcomes was also assessed with stratification by parity.

FINDINGS

17 873 births occurred in the conventional period and 8131 in the integrated period. Compared with the conventional period, women giving birth during the integrated period were slightly older (30·63 years vs 30·88 years) and had slightly higher BMI (25·52 kg/m2vs 26·14 kg/m2), and more Australian-born women gave birth during the integrated period (37·37% vs 39·79%). There were no significant differences in smoking status or parity between the two groups. 107 (0·08%) of 129 514 antenatal consultations in the conventional period and 34 444 (45·94%) of 74 982 in the integrated period were delivered by telehealth. No significant differences between the conventional and integrated periods were seen in median gestational age at pre-eclampsia diagnosis (low-risk models 37·4 weeks in the conventional period vs 37·1 weeks in the integrated period, difference -0·3 weeks [-0·7 to 0·1]; high-risk models 35·5 weeks vs 36·3 weeks, difference 0·3 weeks [-0·3 to 1·1]), incidence of FGR below the 3rd birthweight percentile (low-risk models 1·62% vs 1·74%, difference 0·12 percentage points [-0·26 to 0·50]; high-risk 4·04% vs 4·13%, difference 0·089 percentage points [-1·08 to 1·26]), and incidence of preterm birth (low-risk models 4·99% vs 5·01%, difference 0·02% [-0·62 to 0·66]; high-risk models 15·76% vs 14·43%, difference -1·33% [-3·42 to 0·77]). Parity did not affect these findings. Interrupted time-series analysis showed a significant reduction in induction of labour for singletons with suspected FGR among women in low-risk models during the integrated period (-0·04% change per week [95% CI -0·07 to -0·01], p=0·0040), and NICU admission declined after telehealth integration (low-risk models -0·02% change per week [-0·03 to -0·003], p=0·018; high-risk models -0·10% change per week, -0·19 to -0·001; p=0·047). No significant differences in stillbirth rates were observed. The proportion of women diagnosed with gestational diabetes was significantly higher in the integrated period compared with the conventional period for both low-risk care models (22·28% vs 25·13%, difference 2·85 percentage points [1·60 to 4·11]) and high-risk care models (28·70% vs 34·02%, difference 5·32 percentage points [2·57 to 8·07]). However overall, when compared with the conventional period, there was no significant difference in proportion of women with gestational diabetes requiring insulin therapy (low-risk models 8·08% vs 7·73%, difference -0·35 percentage points [-1·13 vs 0·44]; high-risk models 14·81% vs 15·71%, difference 0·89 percentage points [-1·23 to 3·02]), or proportion of women with gestational diabetes who gave birth to a baby with macrosomia in the integrated period (low-risk models 3·16% vs 2·33%, difference -0·83 percentage points [-1·77 to 0·12]; high-risk models 5·58% vs 4·81%, difference -0·77 percentage points [-3·06 to 1·52]).

INTERPRETATION

Telehealth-integrated antenatal care replaced around 46% of in-person consultations without compromising pregnancy outcomes. It might be associated with a reduction in labour induction for suspected FGR, particularly for women in low-risk models, without compromising FGR detection or perinatal morbidity. These findings support the ongoing use of telehealth in providing flexible antenatal care.

FUNDING

None.

Improving Tdap maternal immunization rate in Saudi Arabia

Pertussis is a serious and potentially fatal disease in infants too young for vaccination. Despite a high vaccine coverage in children, pertussis continues to occur in unvaccinated infants in the Kingdom of Saudi Arabia (KSA). Available data supports the use of maternal pertussis immunization for preventing pertussis in young infants. In June 2019, the Saudi Ministry of Health recommended maternal pertussis immunization with combined tetanus-diphtheria-acellular pertussis vaccine (Tdap) during every pregnancy. To understand barriers to maternal immunization and identify strategies to improve maternal immunization, we conducted an online survey in November and December 2020, asking 60 obstetricians/gynecologists about their attitudes to maternal pertussis immunization. Fewer than 50% survey respondents considered maternal immunization as part of their role, and only 47% were aware of the national recommendation. Consequently, the uptake of maternal vaccination in KSA may be sub-optimal. The key barriers that hinder obstetricians/gynecologists from recommending maternal Tdap immunization were the anticipation of patient refusal, and their own need for more information/experience about the disease and the national recommendation. Vaccine availability and supply were important barriers, whereas cost/reimbursement and resource issues were of lesser concern. Disseminating evidence based information to physicians, educating pregnant women and addressing public misconceptions.

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

INTRODUCTION

Despite a decrease in infections caused by Bordetella pertussis due to COVID-19 pandemic, booster vaccination of pregnant women is still recommended to protect newborns. Highly immunogenic vaccines containing genetically inactivated pertussis toxin (PTgen) and filamentous hemagglutinin (FHA) may generate comparable anti-PT antibody concentrations, even at lower doses, to chemically inactivated acellular pertussis vaccines (Tdapchem) shown effective for maternal immunization.

METHODS

This phase 2 randomized, observer-blind, active-controlled non-inferiority trial was conducted in healthy Thai pregnant women randomly assigned to receive one dose of low-dose recombinant pertussis-only vaccine containing 1 µg PTgen and 1 µg FHA (ap1gen), or tetanus, reduced-dose diphtheria combined with ap1gen (Tdap1gen), or combined with 2 µg PTgen and 5 µg FHA (Tdap2gen), or with 5 µg PTgen and 5 µg FHA (TdaP5gen, Boostagen®) or comparator containing 8 µg of chemically inactivated pertussis toxoid, 8 µg FHA, and 2.5 µg pertactin (Boostrix™, Tdap8chem). Blood was collected at Day 0 and Day 28 post-vaccination. The non-inferiority of the study vaccines was assessed based on anti-PT IgG antibody levels on Day 28 pooled with results from a similarly structured previous trial in non-pregnant women.

RESULTS

400 healthy pregnant women received one dose of vaccine. Combined with data from 250 non-pregnant women, all study vaccines containing PTgen were non-inferior to comparator vaccine (Tdap8chem). Both ap1gen and TdaP5gen vaccines could be considered to have superior immunogenicity to Tdap8chem. Local and systemic solicited reactions were similar among all vaccine groups.

CONCLUSIONS

Vaccine formulations containing PTgen were safe and immunogenic in pregnant women. The ap1gen vaccine, with the lowest cost and reactogenicity, may be suitable for use in pregnant women when diphtheria and tetanus toxoids are not needed. This study is registered in the Thai Clinical Trial Registry (www.

CLINICALTRIALS

in.th), number TCTR20180725004.

Maternal Vaccination to Prevent Adverse Pregnancy Outcomes: An Underutilized Molecular Immunological Intervention?

Adverse pregnancy outcomes including maternal mortality, stillbirth, preterm birth, intrauterine growth restriction cause millions of deaths each year. More effective interventions are urgently needed. Maternal immunization could be one such intervention protecting the mother and newborn from infection through its pathogen-specific effects. However, many adverse pregnancy outcomes are not directly linked to the infectious pathogens targeted by existing maternal vaccines but rather are linked to pathological inflammation unfolding during pregnancy. The underlying pathogenesis driving such unfavourable outcomes have only partially been elucidated but appear to relate to altered immune regulation by innate as well as adaptive immune responses, ultimately leading to aberrant maternal immune activation. Maternal immunization, like all immunization, impacts the immune system beyond pathogen-specific immunity. This raises the possibility that maternal vaccination could potentially be utilised as a pathogen-agnostic immune modulatory intervention to redirect abnormal immune trajectories towards a more favourable phenotype providing pregnancy protection. In this review we describe the epidemiological evidence surrounding this hypothesis, along with the mechanistic plausibility and present a possible path forward to accelerate addressing the urgent need of adverse pregnancy outcomes.

Early-onset group B streptococcal disease in African countries and maternal vaccination strategies

Invasive group B streptococcal (GBS) disease is the commonest perinatally-acquired bacterial infection in newborns; the burden is higher in African countries where intrapartum antibiotic prophylaxis strategies are not feasible. In sub-Saharan Africa, almost one in four newborns with GBS early-onset disease will demise, and one in ten survivors have moderate or severe neurodevelopmental impairment. A maternal GBS vaccine to prevent invasive GBS disease in infancy is a pragmatic and cost-effective preventative strategy for Africa. Hexavalent polysaccharide protein conjugate and Alpha family surface protein vaccines are undergoing phase II clinical trials. Vaccine licensure may be facilitated by demonstrating safety and immunological correlates/thresholds suggestive of protection against invasive GBS disease. This will then be followed by phase IV effectiveness studies to assess the burden of GBS vaccine preventable disease, including the effect on all-cause neonatal infections, neonatal deaths and stillbirths.