Maternal RSVpreF Vaccine and Nirsevimab Show Similar RSV Protection in Full-Term Infants

Maternal respiratory syncytial virus (RSV) vaccination and infant nirsevimab did not differ significantly in protection against RSV infection or hospitalization among full-term infants, according to a retrospective cohort study published in JAMA Network Open and presented at IDWeek 2026.

Since 2023, infants can be protected against RSV through a bivalent RSV prefusion F (RSVpreF) vaccine given during pregnancy or through nirsevimab, a monoclonal antibody given to infants. The investigators noted that the CDC recommends either product without preference, while a single-season French study had reported higher nirsevimab effectiveness against RSV hospitalization.

The analysis included 15,124 matched full-term infants born at Kaiser Permanente Northern California during the 2023-2024 and 2024-2025 RSV seasons whose mothers received RSVpreF at 32 to 36 weeks’ gestation or who received nirsevimab within 7 days of birth. Follow-up ran from age 8 days through 180 days or the end of the RSV season. PCR-confirmed RSV infection, the primary outcome, occurred in 0.94% of the RSVpreF group and 1.04% of the nirsevimab group, with no statistically significant difference (relative product effectiveness [rPE], −5.3%; 95% CI, −44.8% to 23.4%).

Twelve infants had an RSV hospitalization, 7 after RSVpreF and 5 after nirsevimab. Against hospitalization, the rPE of RSVpreF vs nirsevimab was 61.5%, but the confidence interval included no difference (95% CI, −10.8% to 86.7%). Head-to-head results were similar for the 2024-2025 season alone and with follow-up limited to 90 days of age. Compared with matched unprotected infants, RSVpreF was associated with an rPE of 69.3% against infection and 86.4% against hospitalization, and nirsevimab with 65.2% and 73.8%, respectively.

The authors noted that few outcome events limited power to detect small differences, that including only full-term infants limits generalizability to preterm infants, and that the observational design could not account for all differences between those choosing each product. They concluded that the findings support current US guidelines for either maternal RSVpreF or infant nirsevimab to protect all infants from RSV.

Source: Jacobson KB, Watson AJ, Liao LD, et al. Maternal vaccination vs nirsevimab use and respiratory syncytial virus infection among full-term infants. JAMA Netw Open. 2026;9(10):e2636760. doi:10.1001/jamanetworkopen.2026.36760