A recent cohort study found that among pregnant women, prenatal respiratory syncytial virus (RSV) vaccination did not increase the risk of preterm birth, though it indicated a potential increase in hypertensive disorders of pregnancy that requires further investigation.

The study, published in JAMA Network Open, evaluated the safety of administering a nonadjuvanted bivalent RSV prefusion F (RSVpreF) protein subunit vaccine to pregnant women. It investigated the association between prenatal RSV vaccination and preterm birth, as well as other perinatal outcomes, including hypertensive disorders of pregnancy, stillbirth, small-for–gestational age birth weight, neonatal intensive care unit (NICU) admission, neonatal respiratory distress with NICU admission, neonatal jaundice or hyperbilirubinemia, neonatal hypoglycemia, and neonatal sepsis.

The cohort consisted of 2,973 pregnant individuals who delivered singleton pregnancies at 32 weeks’ gestation or later between September 22, 2023, and January 31, 2024. Of these, 1,026 (34.5%) received the RSVpreF vaccine during pregnancy. Median interquartile age of the individuals was 34.9 years (range = 32.4-37.7 years). The mean standard deviation gestational age at time of vaccination was 34.5 (1.4) weeks. The primary outcome was preterm birth, defined as delivery before 37 weeks’ gestation. 

The findings indicated a preterm birth rate of 6.5% among the cohort (191 of 2,973 individuals), with no significant increase in preterm birth risk associated with the RSVpreF vaccination (adjusted odds ratio = 0.87; 95% confidence interval [CI] = 0.62-1.20). Additionally, there were no significant differences in small-for–gestational age birth weight or stillbirth rates between the vaccinated and unvaccinated groups. However, an increased risk of hypertensive disorders of pregnancy was noted in the vaccinated group when accounting for time-dependent factors (hazard ratio = 1.43; 95% CI = 1.16-1.77).

These results indicated that the RSVpreF vaccine during pregnancy was not associated with an increased risk of preterm birth. The observed potential increase in hypertensive disorders of pregnancy risk requires further investigation. Further research and ongoing surveillance are needed to validate these findings and to understand the factors influencing vaccination uptake among different demographic groups.

Full disclosures can be found in the published study.