Infants who received nirsevimab may have a lower risk of hospitalization for respiratory syncytial virus compared with those whose mothers received a vaccine during pregnancy, according to a nationwide study.
In the population-based cohort study using the French National Health Data System, investigators evaluated more than 42,000 newborn patients during the 2024 to 2025 respiratory syncytial virus (RSV) season. The patients were matched 1:1 on the basis of discharge timing, gestational age, sex, and region. One group received nirsevimab shortly following birth, while the comparison group included infantile patients with protection through maternal vaccination with the RSV prefusion F (RSVpreF) vaccine during 32 to 36 weeks’ gestation. Follow-up began at hospital discharge and continued through February 2025.
The primary outcome was hospitalization for RSV-associated lower respiratory tract infection. Secondary outcomes included admission to the pediatric intensive care unit (PICU), admission to a high-dependency unit, ventilatory support, and oxygen therapy.
Among 481 hospitalizations, 44% (n = 212) of them occurred in the nirsevimab group compared with 56% (n = 269) in the maternal vaccination group. Nirsevimab was associated with a 26% lower likelihood of RSV-associated lower respiratory tract infection. Severe outcomes were also less prevalent among the patients who received nirsevimab, including PICU admission, ventilatory support, and oxygen therapy.
Subgroup analyses showed consistent findings across sex, gestational age, and socioeconomic groups. The relative benefit of nirsevimab increased over time, with lower hospitalization risk observed after 30 days and continuing beyond 60 days. During the first week following discharge, hospitalization risk was higher in the nirsevimab group, reflecting differences in the timing of protection between the two approaches.
This study represented one of the first large, real-world comparisons of these two hospitalization prevention strategies during the same RSV season and within the same population. Both approaches have demonstrated efficacy in clinical trials; however, prior to the analysis, direct comparative data in routine clinical use were limited.
The findings should be interpreted with several limitations. As an observational study, residual confounding couldn't be excluded despite matching and statistical adjustment. The analysis reflected a single season during the early implementation of both strategies in France, with follow-up limited to several months. Maternal vaccination was also restricted to a defined gestational window, and the results may not be generalizable to other settings or vaccination practices.
Overall, both strategies were associated with reduced adverse RSV-related outcomes, but infant immunization with nirsevimab was associated with lower rates of hospitalization and severe outcomes during early infancy.
“[T]heir use should be re-evaluated in future studies,” wrote lead study author Marie-Joelle Jabagi, PharmD, PhD, of the French National Agency for Medicines and Health Products Safety as well as French National Health Insurance, and colleagues.
The study was funded by the French National Agency for Medicines and Health Products Safety and the French National Health Insurance. The study authors reported no conflicts of interest.
Source: JAMA