Maternal Vaccination and Infant Influenza and Pertussis

Routine Vaccination During Pregnancy Among People Living With HIV in the United States

Importance

Pregnancy represents a window of opportunity for vaccination due to established maternal and fetal benefits of vaccination. Little is known about receipt of routinely recommended vaccines in pregnancy, specifically tetanus, diphtheria, plus acellular pertussis (Tdap) and influenza, among pregnant people living with HIV (PLHIV).

Objective

To estimate prevalence of vaccination receipt among pregnant people with HIV (PLHIV) and identify demographic and clinical characteristics associated with vaccination.

Design, Setting, and Participants

This multicenter cohort study included women participating in Women's Health Study (WHS) of the Surveillance Monitoring for ART Toxicities (SMARTT) Study of the Pediatric HIV/AIDS Cohort Study. The network has been enrolling pregnant PLHIV at 22 US sites since 2007. Participants for this study enrolled between December 2017 and July 2019. Data analysis was conducted from October 2021 to March 2022.

Exposure

Data on vaccination in pregnancy were collected through medical record abstraction.

Main Outcomes and Measures

Vaccination receipt was defined as Tdap vaccination received at less than 36 weeks' gestation and influenza vaccination at any gestational age, based on current guidelines. Log-binomial and modified Poisson regression models with generalized estimating equations were fit to identify factors associated with successful receipt of (1) Tdap, (2) influenza, and (3) both vaccinations.

Results

A total of 310 pregnancies among 278 people participating in the WHS were included (mean [SD] age, 29.5 [6.1] years; 220 [71%] Black, 77 [25%] Hispanic, and 77 [25%] race and ethnicity other than Black; 64 [21%] with perinatally acquired HIV). Less than one-third of pregnancies were vaccinated as recommended (Tdap, 32.6% [95% CI, 27.4%-38.1%]; influenza, 31.6% [95% CI, 26.5%-37.1%]; both, 22.6% [95% CI, 18.0%-27.6%]). People living with perinatally acquired HIV, those who did not identify as Black, or those who were multiparous had adjusted risk ratios (aRRs) less than 1, while older PLHIV had aRRs greater than 1, but these differences did not reach statistical significance (perinatally acquired HIV: adjusted risk ratio [aRR], 0.46; 95% CI, 0.21-1.02; race other than Black: aRR, 0.53; 95% CI, 0.26-1.08; multiparous: aRR, 0.59; 95% CI, 0.35-1.00; age 24-29 years: aRR, 2.03; 95% CI, 0.92-4.48).

Conclusions and Relevance

In this diverse, multicenter cohort of pregnant PLHIV, receipt of recommended vaccinations was low. Identifying and addressing barriers to vaccination receipt is urgently needed for pregnant people with HIV.

The effectiveness of maternal pertussis vaccination for protecting Aboriginal and Torres Strait Islander infants against infection, 2012-2017: a retrospective cohort study

OBJECTIVES

To evaluate the effectiveness of maternal pertussis vaccination for preventing pertussis infections in Aboriginal and Torres Strait Islander infants under seven months of age.

STUDY DESIGN

Retrospective cohort study; analysis of linked administrative health data.

SETTING, PARTICIPANTS

Mother-infant cohort (Links2HealthierBubs) including all pregnant women who gave birth to live infants (gestational age ≥ 20 weeks, birthweight ≥ 400 g) in the Northern Territory, Queensland, and Western Australia during 1 January 2012 - 31 December 2017.

MAIN OUTCOME MEASURES

Proportions of women vaccinated against pertussis during pregnancy, rates of pertussis infections among infants under seven months of age, and estimated effectiveness of maternal vaccination for protecting infants against pertussis infection, each by Indigenous status.

RESULTS

Of the 19 892 Aboriginal and Torres Strait Islander women who gave birth to live infants during 2012-2017, 7398 (37.2%) received pertussis vaccine doses during their pregnancy, as had 137 034 of 259 526 non-Indigenous women (52.8%; Indigenous v non-Indigenous: adjusted odds ratio, 0.66; 95% confidence interval [CI], 0.62-0.70). The annual incidence of notified pertussis infections in non-Indigenous infants declined from 16.8 (95% CI, 9.9-29) in 2012 to 1.4 (95% CI, 0.3-8.0) cases per 10 000 births in 2017; among Aboriginal and Torres Strait Islander infants, it declined from 47.6 (95% CI, 16.2-139) to 38.6 (95% CI, 10.6-140) cases per 10 000 births. The effectiveness of maternal vaccination for protecting non-Indigenous infants under seven months of age against pertussis infection during 2014-17 was 68.2% (95% CI, 51.8-79.0%); protection of Aboriginal and Torres Strait Islander infants was not statistically significant (36.1%; 95% CI, -41.3% to 71.1%).

CONCLUSIONS

During 2015-17, maternal pertussis vaccination did not protect Aboriginal and Torres Strait Islander infants in the NT, Queensland, and WA against infection. Increasing the pertussis vaccination rate among pregnant Aboriginal and Torres Strait Islander women requires culturally appropriate, innovative strategies co-designed in partnership with Indigenous organisations and communities.

Characteristics and Outcomes of Pregnant Women Hospitalized With Laboratory-Confirmed Respiratory Syncytial Virus Before and During the COVID-19 Pandemic

Background

Respiratory syncytial virus (RSV) can cause severe disease among infants and older adults. Less is known about RSV among pregnant women.

Methods

To analyze hospitalizations with laboratory-confirmed RSV among women aged 18 to 49 years, we used data from the RSV Hospitalization Surveillance Network (RSV-NET), a multistate population-based surveillance system. Specifically, we compared characteristics and outcomes among (1) pregnant and nonpregnant women during the pre-COVID-19 pandemic period (2014-2018), (2) pregnant women with respiratory symptoms during the prepandemic and pandemic periods (2021-2023), and (3) pregnant women with and without respiratory symptoms in the pandemic period. Using multivariable logistic regression, we examined whether pregnancy was a risk factor for severe outcomes (intensive care unit admission or in-hospital death) among women aged 18 to 49 years who were hospitalized with RSV prepandemic.

Results

Prepandemic, 387 women aged 18 to 49 years were hospitalized with RSV. Of those, 350 (90.4%) had respiratory symptoms, among whom 33 (9.4%) were pregnant. Five (15.2%) pregnant women and 74 (23.3%) nonpregnant women were admitted to the intensive care unit; no pregnant women and 5 (1.6%) nonpregnant women died. Among 279 hospitalized pregnant women, 41 were identified prepandemic and 238 during the pandemic: 80.5% and 35.3% had respiratory symptoms, respectively (P < .001). Pregnant women were more likely to deliver during their RSV-associated hospitalization during the pandemic vs the prepandemic period (73.1% vs 43.9%, P < .001).

Conclusions

Few pregnant women had severe RSV disease, and pregnancy was not a risk factor for a severe outcome. More asymptomatic pregnant women were identified during the pandemic, likely due to changes in testing practices for RSV.

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.

Coverage and predictors of influenza and pertussis vaccination during pregnancy: a whole of population-based study

BACKGROUND

Respiratory infections including influenza and pertussis are associated with significant morbidity and mortality in mothers and newborns. Vaccination during pregnancy against influenza and pertussis is recommended for all women but data on uptake in Australia is limited.

METHODS

We conducted a retrospective population-based cohort study in Australia's largest state, New South Wales (NSW), using a Perinatal Data Collection (PDC). Data included demographic, pregnancy, and birth details including pertussis and influenza vaccination during pregnancy for all women giving birth between 01 January 2016 and 31 December 2020. We used descriptive statistics to assess uptake of influenza and pertussis vaccination during pregnancy and Poisson loglinear regression to estimate associations between maternal characteristics and vaccine receipt.

RESULTS

During 2016-2020, there were 477,776 births (mean maternal age 32.25 years). In 176,255 (36.9%) births the mother received both vaccines; 202,922 (42.5%) influenza and 315,620 (66.1%) pertussis vaccine. From 2016 to 2020, reported coverage increased from 26.7% to 58.7% for influenza and 43.1% to 78.8% for pertussis, respectively. After adjustment, characteristics associated with lower likelihood of receiving influenza and pertussis vaccination included: younger age (<30 years), being born in Australia/New Zealand, from lower socio-economic strata, having previous pregnancies, being later to first antenatal care, utilising the public hospital care model, smoking, having chronic hypertension and BMI > 25 kg/m2.

CONCLUSIONS

While reported coverage of both influenza and pertussis vaccine in birthing women in NSW has increased over time, disparities in coverage exist and they highlight areas where evidence-based interventions to improve maternal vaccination could be targeted.

Effectiveness of maternal immunisation with a three-component acellular pertussis vaccine at preventing pertussis in infants in the United States: Post-hoc analysis of a case-control study using Bayesian dynamic borrowing

BACKGROUND

Immunisation during pregnancy with a tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine can protect infants against pertussis between birth and paediatric vaccination. We aimed to estimate the vaccine effectiveness (VE) of third-trimester pregnancy immunisation with the three-component acellular pertussis (Td3ap) vaccine at preventing pertussis in infants <2 months in the United States (US), to support a label update.

METHODS

We performed a post-hoc sub-analysis of a case-control study conducted in six US Emerging Infections Program Network states between 2011 and 2014. Our analysis included only cases and controls whose mothers were either vaccinated with Td3ap or did not receive any Tdap vaccine. The association between Td3ap maternal immunisation and pertussis in infants was assessed for US data using a frequentist method with conditional logistic regression. A robustified analysis was conducted using Bayesian dynamic borrowing of non-US data, considering a mixing-weighted prior of 90% for historical non-US VE data, and of 10% for a vague prior. VE was estimated as (1-odds ratio) × 100%. Sensitivity analyses accounting for the impact of each non-US study, different mixing weights and missing/ambiguous data were performed.

RESULTS

We included 108 cases and 183 controls. Based on US data, the estimated VE of third-trimester maternal immunisation with Td3ap at preventing pertussis in infants <2 months was 78.0% (95% confidence interval: -38.0; 96.5). VE estimated by Bayesian dynamic borrowing of non-US data (with a 90% weight for historical data) was 83.4% (95% credible interval: 55.7; 92.5); sensitivity analyses produced similar VE estimates.

CONCLUSIONS

Effectiveness of third-trimester pregnancy immunisation with Td3ap at preventing infant pertussis in the US is very likely to be ≥ 50% and is most likely ∼ 80%. Bayesian dynamic borrowing of non-US VE data allowed overcoming the limited power (due to small sample size) of a brand-specific sub-analysis by considering additional evidence.

The association between vaccine hesitancy and pertussis: a systematic review and meta-analysis

BACKGROUND

Robust routine immunization schedules for pertussis-containing vaccines have been applied for years, but pertussis outbreaks remain a worldwide problem. This study aimed to investigate the association between vaccine hesitancy and pertussis in infants and children.

METHODS

We searched PubMed, Cochrane, Web of Science, Embase, and China National Knowledge Internet for studies published between January 2012 and June 2022. This study included case-control and cohort studies that assessed the association between childhood/maternal vaccine hesitancy and odds ratios (ORs), risk ratios (RRs), and vaccine effectiveness (VE) related to pertussis in infants and children [Formula: see text] 9 years old. ORs/VEs with a 95% confidence interval (CI) were calculated. Random-effects meta-analysis models were used for appropriate pooled estimates, and heterogeneity was assessed using [Formula: see text]. Cumulative meta-analysis and subgroup analyses stratified by study characteristics were performed.

RESULTS

Twenty-two studies were included, with a mean quality score of 7.0 (range 6.0-9.0). Infants and children with pertussis were associated with higher vaccine hesitancy to all doses (OR = 4.12 [95% CI: 3.09-5.50]). The highest OR was between children who were unvaccinated over four doses and children who were fully vaccinated (OR = 14.26 [95%CI: 7.62-26.70]); childhood vaccine delay was not statistically significantly associated with pertussis risk (OR = 1.18 [95% CI: 0.74-1.89]). Maternal vaccine hesitancy was associated with significantly higher pertussis risk in infants aged 2 and 3 months old, with higher pertussis ORs in infants [Formula: see text] 2 months old (OR = 6.02 [95%CI: 4.31-8.50], OR = 5.14 [95%CI: 1.95-13.52] for infants [Formula: see text] 2 and [Formula: see text] 3 months old, respectively). Maternal and childhood VEs were high in reducing pertussis infection in infants and children. The administration time of maternal vaccination had little effect on VE.

CONCLUSION

Vaccine hesitancy increased pertussis risks in infants and children. Ensuring that children receive up-to-date pertussis vaccines is essential; short delays in receiving childhood vaccinations may be unimportant. Maternal vaccinations for pertussis should be encouraged.

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

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

Factors Influencing Maternal Antepartum Tdap Vaccination

INTRODUCTION

Antepartum Tdap remains low despite national recommendations. This prospective observational study aims to identify factors associated with lower antepartum Tdap rates.

METHODS

Maternal demographics, personal health beliefs, Tdap vaccination status, and recall of in-office obstetric provider actions were collected from a convenience sample of postpartum women in a New York metropolitan hospital. Bivariate and multivariable logistic regression were used to identify significant factors and adjusted odds ratios (OR) for recorded Tdap; OR > 1 reflects elements with increased odds of not receiving antepartum Tdap, while OR < 1 demonstrates increased odds of receipt.

RESULTS

Surveys were collected (n = 1682) from a study population demographically similar to New York City and more diverse in race/ethnicity than the national population. Demographic analysis showed Hispanic women less likely than white, non-Hispanic women to vaccinate (OR 2.44, CI 1.54-3.88). Health beliefs associated with non-receipt of antepartum Tdap included "It is dangerous for pregnant women to get vaccines" (OR 1.68, CI 1.01-2.77), and "I worry about the safety of the Tdap vaccine" (OR 1.59, CI 1.12-2.24). Obstetric provider actions associated with vaccination included receiving an OB recommendation (OR 0.39, CI 0.23-0.65), getting written information about Tdap (OR 0.44, CI 0.30-0.64), and having Tdap offered in office (OR 0.24, CI 0.15-0.37). Health beliefs associated with antepartum Tdap included "I generally do what my OB/GYN provider recommends" (OR 0.49, CI 0.30-0.80), and "Pregnant women should get the Tdap (pertussis) vaccine" (OR 0.17, CI 0.09-0.33).

DISCUSSION

Maternal race/ethnicity, personal health beliefs, and obstetric provider actions predict antepartum Tdap.