Monoclonal Antibodies in RSV Prevention: Potential Game-Changer for Infant Health

A recent study found that nirsevimab reduced RSV-related hospitalizations by 79% overall, substantially lowering severe infant outcomes during the winter season. This magnitude of effect argues for rapid integration of infant immunization into seasonal RSV programs and delivery pathways. The finding shifts the prevention landscape by providing a direct, infant-targeted prophylactic option that can be given at or shortly after birth to blunt early severe disease.

The evidence derives from a multicountry study in Belgium, Portugal and Spain that enrolled more than 2,200 children under two years and used RSV-related hospitalization as the primary endpoint.

Effectiveness was 80% in infants aged 0–6 months, identifying the youngest infants as the group with the greatest relative benefit during their highest-risk interval. Protection was highest in the first month after immunization (≈85%) and declined to about 69% by three months; the protection profile of this long-acting monoclonal antibody therefore shows meaningful waning across the early post-immunization period. That time course directly informs choices about timing of administration and seasonal targeting to cover peak exposure months.

Operational planning should prioritize administering a single seasonal dose to infants younger than six months at the start of the RSV season, with delivery routes focused on pediatric clinics and discharge planning units. Near-term monitoring of durability and population-level effectiveness is warranted to refine the timing window, consider thresholds for repeat dosing if needed, and evaluate potential indirect effects on community transmission. Infants under six months, particularly neonates entering their first RSV season, will derive the greatest immediate benefit from prioritized seasonal monoclonal antibody delivery.