Effectiveness of nirsevimab against hospitalisation for RSV-bronchiolitis during high RSV-B circulation in the second year of nationwide implementation in France: a test-negative case-control study.
case_control · Level III
Where this comes from
- Record sourced from PubMed, PMID 41220615.
- Also identified by DOI 10.1016/j.lanepe.2025.101443 and PMC identifier 12598395.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Nirsevimab was first introduced in September 2023, showing strong real-world effectiveness in preventing hospitalised RSV-bronchiolitis. RSV-A circulation predominated during 2023-2024, whereas RSV-B was frequent in 2024-2025. Recent reports indicated resistance to nirsevimab in RSV-B strains in France. We aimed to assess the effectiveness of large-scale nirsevimab implementation against hospitalised RSV-bronchiolitis during high RSV-B circulation. A test-negative case-control study was conducted using a national hospital-based surveillance system. All children <12 months hospitalised for bronchiolitis and tested for RSV in 12 French hospitals from October 10, 2024 to March 15, 2025, were included. Cases were RSV-positive bronchiolitis; controls were RSV-negative bronchiolitis. Effectiveness was assessed by a multivariable logistic regression model adjusted for confounders (sex, gestational age at birth, birth weight, risk factors for severe bronchiolitis, month of diagnosis, and medical centre). A range of sensitivity analyses was conducted. 1270 patients were included; among which 830 (65.3%) were RSV-positive and 440 (34.7%) were RSV-negative bronchiolitis. The male-to-female sex ratio was 1.35, and the median age was 3 months (IQR: 1.5-5.6). Among cases, 182 (22.0%) received nirsevimab, compared to 282 (64.1%) for controls. Adjusted effectiveness against RSV-bronchiolitis was 84.9% (95% CI, 80.0-88.6). Subgroup analyses by age and severity (intensive care unit admission, respiratory support) showed consistent results, along with sensitivity analyses. Despite high RSV-B circulation, which has recently been identified to carry mutations potentially inducing resistance to nirsevimab, the effectiveness of the second national nirsevimab campaign against hospitalisation for RSV-bronchiolitis remained high. The study received financial support from Sanofi, AstraZeneca, and the 2023 ATIP-Avenir grant from the National Institute of Health and Medical Research (Inserm).