For parents and pediatricians navigating two newly available RSV prevention strategies, the critical question has shifted from 'does it work?' to 'which works better?' A large French national cohort study now offers the first real-world comparative effectiveness data between nirsevimab—a monoclonal antibody given directly to newborns—and RSVpreF, the maternal vaccine administered during pregnancy, with implications for how national immunization programs should be structured.
Drawing on the French National Health Data System, this retrospective cohort study enrolled 164,140 infants born between September 2024 and February 2025—a full RSV season—whose protection derived either from nirsevimab administered at birth or from transplacental antibodies conferred by maternal RSVpreF vaccination between gestational weeks 28 and 36. The primary outcome was RSV-related lower respiratory tract infection (LRTI) hospitalization before six months of age. Propensity score matching on birth date, region, and sex was used to control for confounding, with secondary analyses examining how vaccination timing during pregnancy influenced maternal vaccine effectiveness.
This study is notable for its scale and real-world design at a moment when both products are newly deployed and head-to-head randomized trial data do not yet exist. The critical methodological caveat is its observational, retrospective nature: families who opted for each strategy almost certainly differ in clinically meaningful ways—healthcare access, prematurity rates, socioeconomic factors—that propensity scoring may not fully resolve. Timing of maternal vaccination relative to delivery is also an important confounder, since antibody transfer efficiency diminishes with shorter intervals between immunization and birth. The finding that vaccination timing during pregnancy modified outcomes underscores that maternal immunization effectiveness is highly sensitive to program logistics. For public health planners, these data suggest nirsevimab's postnatal delivery model may offer more consistent protection across diverse populations, though cost-effectiveness and access equity analyses remain essential before definitive programmatic recommendations can follow. Incrementally confirmatory on nirsevimab's potency; more novel in establishing a direct comparative benchmark.