Evaluating the Uptake, Safety and Effectiveness of the Maternal RSV Vaccine (RSVpreF) Against Infant Bronchiolitis: Preliminary Real-World Evidence

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of infant hospitalization globally. On September 1, 2024, England introduced the bivalent RSVpreF vaccine for maternal immunization following trial evidence of safety and efficacy. However, real-world data on uptake, safety and effectiveness remain limited. METHODS: We conducted a retrospective audit using routinely collected electronic health record data from Oxford University Hospitals NHS Foundation Trust. All live births between September 1 and October 31, 2024, were included. Maternal RSV vaccination status, demographic factors and perinatal outcomes were analyzed. RSV-related hospitalizations were tracked from November 1, 2024, to March 12, 2025. Vaccine effectiveness (VE) was calculated as 1 - (risk in vaccinated/risk in unvaccinated) × 100. RESULTS: Among 1057 live births, 341 mothers (32.3%) received RSVpreF vaccination during pregnancy. Uptake was higher in older and primiparous mothers and strongly associated with receipt of pertussis vaccine (41.3% vs. 11.6%; P < 0.001). No differences were observed in gestational age or birthweight between groups. RSV-confirmed hospitalization occurred in 2 of 285 infants born >14 days post-vaccination and in 36 of 772 unvaccinated infants, yielding a crude VE of 78.3% (95% confidence interval, 9.1-94.8) in infants <6 months of age. VE against bronchiolitis-coded admissions was 56.4% (95% confidence interval, 13.1-78.2). CONCLUSIONS: Maternal RSV vaccination was associated with substantial protection against infant RSV hospitalization during the first UK season of implementation. Uptake improved over time but remained relatively low. Early safety data are reassuring. Continued surveillance and larger multisite evaluations are needed to support national program monitoring and integration.