P4.046: Maternal RSVpreF Vaccination Uptake, Disparities, and Associated Neonatal Outcomes in a Connecticut Hospital Network: Insights from an September 2023–March 2025 Birth Cohort

Background: Respiratory syncytial virus (RSV) is the leading cause of hospitalizations among infants in the United States. In 2023, the FDA licensed the RSVpreF maternal vaccine for the prevention of RSV disease in infants. While pivotal clinical trials confirmed efficacy, non-statistically significant trends were observed that suggested increases in preterm birth, low birthweight (≤2500 g), and neonatal jaundice among vaccine recipients compared to placebo. Monitoring of these neonatal outcomes using real-world data post-licensure is critically needed.

Methods: This descriptive, retrospective cohort study analyzed real-world data from delivery, neonatal, and immunization records across four hospitals in Connecticut. Women who delivered between September 1, 2023, and March 31, 2025 during the winter season (September-March), at ≥ 32 weeks of gestation were included. Sociodemographic characteristics, along with maternal and neonatal outcomes, were compared between those who received RSVpreF immunization and those who did not. Differences between groups were assessed using Chi-squared and Mann-Whitney U tests for categorical or continuous variables, respectively.

Results: Among 13,418 women (median [IQR] age at delivery: 32 [29-36] years), 1,965 (14.6%) received RSV immunization. Immunization rates were higher among women aged ≥35 years (36.4% vs. 33.0%, p=0.012) and nulliparous women (45.1% vs. 41.0%, p< 0.001). Significant sociodemographic disparities were noted: non-Hispanic Black women were underrepresented among vaccine recipients (10.2% vs. 12.4%, p< 0.001) compared to women who did not receive the vaccine. Immunized women were also more likely to be privately insured (64.1% vs. 60.1%, p=0.003), and employed (68.8% vs. 67.5%, p=0.032), compared to unvaccinated women. Delivery and neonatal outcomes showed some differences between groups. Preterm birth was less frequent among immunized women (6.2% vs. 8.8%, p< 0.001). Birth weight (median 3,330g vs. 3,310g, p=0.056), rates of small-for-gestational-age (6.4% vs. 6.6%, p=0.799), and neonatal jaundice (15.8% vs. 16.6%, p=0.379) did not differ significantly. Infant survival rates were comparable between groups, with fetal and neonatal demise occurring in less than 0.2% of cases.

Conclusion: This large, real-world study provides important data on maternal and neonatal outcomes following RSVpreF vaccination during pregnancy. Notably, and providing reassurance counter to initial signals from clinical trials, we observed a significantly lower rate of preterm birth among vaccinated women in this cohort. The overall neonatal safety profile appears favorable. However, identified sociodemographic disparities in vaccine uptake highlight the urgent need for targeted public health strategies and provider communication efforts to promote equitable vaccine access and uptake. These findings support recommendations for continued post-licensure safety monitoring and emphasize the importance of ongoing research to ensure the safe, effective, and equitable use of the maternal RSVpreF vaccine.