Real-world data suggest nirsevimab reduces RSV test-positivity up to 12 months but not beyond — cautious interpretation required

Highlight

– Multicentre TriNetX analysis (Kitano et al., 2025) examined association between timing of last nirsevimab dose and RSV test-positivity among children <24 months tested for RSV (Jul 2023–Jun 2025).
– Receiving nirsevimab within 6 months of testing halved the odds of a positive RSV test (OR 0.49; 95% CI 0.42–0.57); protection persisted, though attenuated, when dose was 6–11 months prior (OR 0.67; 95% CI 0.48–0.94).
– No significant protective association was seen when last dose was >12 months before testing (OR 1.21; 95% CI 0.89–1.65). Findings are hypothesis generating and limited by confounding and database constraints.

Background and disease burden