Peer-reviewed article
Long-term impact of nirsevimab on prevention of respiratory syncytial virus infection using a real-world global database.
Kitano T, Tsuzuki S, Fukuda H, Yoshida S ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study examined how long nirsevimab, an antibody treatment, protects infants under 24 months from respiratory syncytial virus (RSV) infection. Using data from a global database of over 216,000 children, researchers compared RSV infection rates in infants who received nirsevimab at different times before testing. The treatment provided strong protection for up to 12 months after administration but showed no protective benefit beyond that time period.
Key points
- Nirsevimab reduced RSV infection risk by 51% when given within 6 months of testing (OR 0.49)
- Protection was maintained at 6-11 months after administration with 33% risk reduction (OR 0.67)
- No significant protective effect was observed beyond 12 months after nirsevimab administration (OR 1.21)
- Study included 4,627 children receiving nirsevimab within 6 months and 210,626 unvaccinated children for comparison
- Data covered RSV testing between July 2023 and June 2025 across multiple global centres
Limitations
The study was retrospective using observational data, which means causation cannot be definitively established and unmeasured confounding factors may have influenced results. The authors note the results require cautious interpretation due to important limitations, though specific limitations are not detailed in this abstract.
Abstract
Objective The preventive effect of nirsevimab, a long-acting monoclonal antibody, on infants with respiratory syncytial virus (RSV) infection beyond six months has rarely been evaluated. The objective of this study was to evaluate the preventive effects of nirsevimab beyond 6 months after RSV infection using a global database. Methods This was a multi-centre retrospective study using a global database (TriNetX). The participants were children under 24 months of age who required nucleic acid testing for RSV between July 2023 and June 2025. Children who received the last dose of nirsevimab within 6 months, between 6 and 11 months, and beyond 12 months were compared with those who did not receive any nirsevimab dose by epidemic season after propensity score matching. Results A total of 4627, 861, and 532 children aged <24 months who received nirsevimab within 6 months, between 6 and 11 months, and beyond 12 months before RSV testing, respectively, and 210,626 children who did not receive any nirsevimab were identified. Compared with those who did not receive nirsevimab, the odds ratios (OR) of a positive RSV test result among those who received nirsevimab within 6 months, between 6 and 11 months, and beyond 12 months before testing were 0.49 [95% confidence interval (CI) 0.42, 0.57] (p<0.001), 0.67 [0.48, 0.94] (p<0.020), and 1.21 [0.89, 1.65] (p=0.234) in the last epidemic season, respectively. Conclusion This study indicated that the preventive effect of nirsevimab against RSV infection was maintained for up to 12 months following administration, whereas a preventive effect beyond 12 months was not observed. The results of this study need to be interpreted with caution owing to some important limitations.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- Nirsevimab, a long-acting monoclonal antibody administered as a preventive treatment
- Population
- Children under 24 months of age who underwent nucleic acid testing for RSV; compared groups who received nirsevimab at different time intervals (within 6 months, 6-11 months, beyond 12 months) versus those who received no nirsevimab
Key finding
Within 6 months of nirsevimab: OR 0.49 (95% CI 0.42-0.57, p<0.001) - 51% reduction in RSV infection risk
T et al. · Europe PMC · 7 Nov 2025