SAFETY AND IMMUNOGENICITY OF MATERNAL INFLUENZA AND TDAP VACCINATION: A PROSPECTIVE COHORT ANALYSIS OF NEONATAL OUTCOMES

Dr. Camila Morales; MD; Prof. Diego Vargas; MD

Abstract

Maternal immunization represents a pivotal strategy for protecting both the mother and the neonate from vaccine-preventable diseases via the transplacental transfer of maternal antibodies. This study evaluates the clinical safety profiles and immunogenic responses of influenza and Tdap (tetanus-diphtheria-acellular pertussis) vaccinations within a diverse cohort of pregnant individuals. Historically, concerns regarding fetal adverse events have limited vaccine uptake; however, emerging data suggests vigorous immune responses and substantial neonatal protection. This investigation monitors localized and systemic adverse reactions, pregnancy outcomes, and cord blood antibody titers. By quantifying the correlation between maternal antibody levels at delivery and neonatal titers, we establish the efficacy of passive immunity frameworks. Furthermore, the study addresses the timing of vaccination in the second versus third trimester to optimize antibody transfer. Our findings provide a robust evidentiary basis for current immunization guidelines, highlighting the lack of significant obstetric complications associated with these interventions. The data reinforces maternal vaccination as a safe, highly effective procedure for mitigating early infancy morbidity and mortality, advocating for integrated obstetric care policies globally.

Keywords: Maternal Immunization, Transplacental Antibody Transfer, Tdap Vaccine, Influenza Vaccination, Neonatal Immunity, Obstetric Safety, Passive Immunization, Prenatal Care

Neonates are highly susceptible to respiratory infections such as pertussis and influenza due to their immature immune systems and the delay in primary vaccination series. Maternal immunization provides a crucial bridge of protection via passive antibody transfer. Despite the proven benefits, vaccine hesitancy persists among expectant mothers and some healthcare providers due to perceived risks of fetal harm. This research provides contemporary, high-resolution data on the safety and efficacy of common maternal vaccines. By demonstrating the lack of association between vaccination and adverse pregnancy outcomes, and quantifying the robust neonatal antibody levels achieved, this study informs clinical practice and health policy. Strengthening the evidence base is essential for increasing vaccination coverage, ultimately reducing neonatal hospitalizations and mortality associated with vaccine-preventable diseases. This work aligns with global health initiatives to optimize maternal-child health outcomes through preventive medicine.

This study aims to evaluate the safety profile and immunogenic efficacy of maternal influenza and Tdap vaccination, specifically quantifying transplacental antibody transfer ratios and identifying any correlation with adverse neonatal outcomes.

A prospective observational cohort study was conducted across three tertiary maternity centers, enrolling 840 pregnant individuals aged 18–45. Participants were categorized into three groups: those receiving Tdap and Influenza vaccines (n=412), those receiving only one (n=228), and an unvaccinated control group (n=200). Safety was assessed through a 14-day post-vaccination diary and electronic health record monitoring for obstetric complications (preeclampsia, preterm birth, gestational diabetes). Immunogenicity was measured via Enzyme-Linked Immunosorbent Assay (ELISA) to determine IgG titers against Bordetella pertussis toxin (PT) and influenza hemagglutinin (HA) in maternal serum at delivery and umbilical cord blood at birth. The transplacental transfer ratio (TR) was calculated as the cord/maternal titer. Statistical significance was determined using t-tests and multivariable logistic regression, adjusting for maternal age, BMI, and gestational age at vaccination. Data were analyzed using R version 4.2.0, with significance set at p<0.05.

Among the 840 participants, vaccination was not associated with an increased risk of preterm birth (OR 0.94, 95% CI: 0.72–1.21, p=0.62) or low birth weight (OR 1.02, 95% CI: 0.81–1.30, p=0.88). Localized reactions (soreness) were reported by 64% of vaccinees, but systemic febrile reactions occurred in only 3.2%. Immunogenicity analysis revealed a mean Tdap-PT IgG cord blood titer of 48.2 IU/mL in the vaccinated group versus 5.1 IU/mL in the control group (p<0.001). The mean transplacental transfer ratio (TR) was 1.42 for Tdap and 1.28 for Influenza. Vaccinations administered between 27 and 32 weeks of gestation resulted in significantly higher cord blood titers compared to those administered after 36 weeks (p=0.014). For influenza, 88% of infants born to vaccinated mothers achieved seroprotective titers (HI ≥1:40), compared to 14% in the control cohort. No cases of neonatal pertussis were observed in the vaccinated cohort during the 6-month follow-up.

Maternal vaccination with influenza and Tdap vaccines is both safe and highly immunogenic during pregnancy. The findings confirm that high-titer maternal antibodies are efficiently transferred to the fetus, providing a critical window of protection during the first months of life when infants are most vulnerable. The absence of significant differences in obstetric complications between vaccinated and unvaccinated groups mitigates safety concerns that often contribute to vaccine hesitancy. Moreover, the superior transfer ratios observed with early third-trimester vaccination suggest that timing is a crucial factor in maximizing neonatal passive immunity. These results support the universal recommendation of maternal immunization as a standard of care in obstetric practice to reduce the global burden of neonatal infectious diseases. High uptake should be prioritized through clinician-led education and integrated prenatal services.