- Design
- Commentary and interpretation of a population-based observational programme evaluation
- Population
- Infants offered universal nirsevimab in Galicia, Spain
- Primary outcome
- RSV lower respiratory tract infection hospital admissions
- Effect
- Reduction 85.9% (80.2–90.0) in season one; 55.3% (22.5–74.3) in season two
The NIRSE-GAL programme in Galicia, Spain, offered nirsevimab, a long-acting monoclonal antibody against respiratory syncytial virus, to all infants. In the first season it was associated with an 85.9% reduction in RSV lower respiratory tract infection admissions (95% CI 80.2–90.0). This Lancet Infectious Diseases piece focuses on the second season, when the antibody should have largely waned: admissions remained 55.3% lower (22.5–74.3), with fewer recurrent severe episodes.
There was no sign of enhanced disease after prophylaxis, and no shift of severe illness to older ages — a concern with any intervention that delays first infection. The authors offer several possible explanations, including protection of developing lungs during a vulnerable window and a modest lingering drug level.
The second-season finding is observational, comes from one region, and has not been replicated. Its interpretation rests on the assumption that the children spared in season one were the ones who would otherwise have been admitted in season two. Nirsevimab's regulatory status and availability in India are not established in the candidate record.
- Universal infant nirsevimab was associated with large first-season reductions in RSV admissions in a real-world programme.
- No enhanced disease or age shift in severity was seen after prophylaxis, which addresses a common worry.
- Treat the second-season benefit as a signal awaiting replication, not an established effect.
- Families asking about RSV prevention can be told the first-season evidence is strong.
Why it matters
If the second-season effect holds, the value of a single dose has been underestimated.
Don't overread it
The second-season benefit is observational, from one region, and not yet replicated.
The statistics, in plain English
A 55.3% reduction with a 95% confidence interval of 22.5% to 74.3% is wide: the true second-season effect could be modest or large. Programme data compare periods and populations rather than randomised groups, so other changes over time could contribute.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for infectious diseases, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free