Maternal Respiratory Syncytial Virus Vaccination and Preterm Birth: A Utah Statewide Retrospective Cohort Study.

We conducted a statewide, retrospective cohort study to evaluate the association between maternal receipt of the respiratory syncytial virus (RSV) vaccine and preterm birth. All individuals who delivered a singleton neonate in Utah and were between 32 0/7 and 36 6/7 weeks of gestation from September 2023 to February 2024 were included and followed up until delivery. Overall, 2,733 of 24,213 individuals (11.3%) received the vaccine. Vaccine receipt was associated with lower odds of preterm birth (5.5% vaccinated group vs 6.8% unvaccinated group, adjusted odds ratio 0.80, 95% CI, 0.67-0.95). Receipt of the RSV vaccine was not associated with any adverse birth outcomes, including hypertensive disorders of pregnancy, low birth weight, or fetal or infant death. These findings support the safety of this vaccine in pregnancy, which is known to prevent neonatal severe lower respiratory tract disease.