TOPLINE:

During the first respiratory syncytial virus (RSV) season in France, passive infant immunisation with nirsevimab was associated with a lower risk for hospitalisation for RSV-related lower respiratory tract infection and other severe outcomes than maternal RSV prefusion F protein (RSVpreF) vaccination.

METHODOLOGY:

• Researchers in France conducted a population-based cohort study comparing associations of maternal RSVpreF vaccination vs passive infant immunisation with nirsevimab in preventing RSV-related hospitalisation in infants during the 2024-2025 RSV season.
• A total of 21,280 infants born to mothers vaccinated with the RSVpreF vaccine at 32-36 weeks of gestation (mean age at maternity discharge, 3.8 days; 51.7% boys) were matched with an equal number of infants who received nirsevimab during the maternity stay on the basis of maternity discharge date, sex, gestational age, and region.
• The primary outcome was hospitalisation for RSV-associated lower respiratory tract infection; secondary outcomes included admission to a paediatric ICU or a high-dependency unit, ventilator support, and supplemental oxygen therapy.
• The median follow-up duration was 84 days, beginning on the day of discharge from the birth hospitalisation.

TAKEAWAY:

• Overall, 481 hospitalisations for RSV-associated lower respiratory tract infection occurred, with 44.1% occurring in the nirsevimab group vs 55.9% occurring in the RSVpreF vaccine group (between-group difference, -11.8%; 95% CI, -18.1% to -5.5%).
• Passive infant immunisation with nirsevimab was associated with a 26% lower risk for hospitalisation for RSV-associated lower respiratory tract infection than maternal RSVpreF vaccination (adjusted hazard ratio [aHR], 0.74; 95% CI, 0.61-0.88).
• Compared with maternal RSVpreF vaccination, passive infant immunisation with nirsevimab was associated with a reduced risk for paediatric ICU admission (aHR, 0.58; 95% CI, 0.42-0.80); however, admission to a high-dependency unit did not differ significantly (aHR, 0.87; 95% CI, 0.60-1.25).
• The nirsevimab group also had significantly lower rates of ventilator support and hospitalisations requiring oxygen therapy.

IN PRACTICE:

"This study compared outcomes after passive immunization with nirsevimab vs RSVpreF vaccination, and its findings should not be interpreted as evidence against the efficacy of the RSVpreF vaccine," the authors wrote.

SOURCE:

This study was led by Marie-Joelle Jabagi, PharmD, PhD, French National Agency for Medicines and Health Products Safety and French National Health Insurance, Paris, France. It was published online on December 22, 2025, in JAMA.

LIMITATIONS:

This study spanned only one RSV season; therefore, it could not assess the durability of protection. Because the vaccine launched in September and matching was based on birth dates, infants born earlier in the RSV season may be underrepresented, which may have limited generalisability. The analysis reflected France's first season of maternal vaccination restricted to 32-36 weeks of gestation; however, guidelines recommend vaccination starting at 28 weeks of gestation.

DISCLOSURES:

This study was funded by the French National Agency for Medicines and Health Products Safety and the French National Health Insurance. The authors reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.