- Design
- Commentary on a population-based observational programme evaluation
- Population
- Infants in Galicia, Spain, offered universal nirsevimab
- Primary outcome
- RSV lower respiratory tract infection hospitalisation
- Effect
- First season −85.9% (95% CI 80.2–90.0); second season −55.3% (22.5–74.3)
A Lancet Infectious Diseases commentary revisits the Galician NIRSE-GAL programme, in which nirsevimab was offered to all infants. In the first season, RSV lower respiratory tract infection admissions fell by 85.9% (95% CI 80.2–90.0). Into the second season, a reduction of 55.3% (22.5–74.3) persisted, alongside fewer repeat severe episodes.
There was no sign of enhanced disease or of severe illness simply shifting to older ages — a reassurance worth having, since nirsevimab does not give sterilising immunity.
Why protection might outlast the antibody is not known. The authors propose that sparing a developing lung from severe infection in the first year, and protecting the most susceptible infants, may matter. They are clear the second-season finding is unreplicated and rests on an unproven assumption about who would have been admitted.
- Universal infant nirsevimab was associated with about 86% fewer first-season RSV admissions
- A second-season reduction of about 55% was seen but has not been replicated
- There was no evidence of enhanced disease after prophylaxis
- Do not promise parents protection beyond the first season on this evidence
Why it matters
It removes the fear that passive protection in infancy merely postpones severe RSV to the next winter.
Don't overread it
The second-season effect comes from one observational programme and has not been replicated.
The statistics, in plain English
The second-season confidence interval, 22.5% to 74.3%, is wide: the true reduction could be modest or large. The first-season interval is narrow, so that estimate is much firmer.
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