Overview

• The multinational analysis compared bronchiolitis outcomes in infants across 68 Catalan hospitals and five centers in the UK and Italy.
• In Catalonia, where nirsevimab was introduced in the 2023–24 season, bronchiolitis admissions for infants under six months dropped by nearly 50%.
• Emergency department attendances for bronchiolitis also declined sharply in the same age group, while non-user centers saw stable rates.
• Protective benefits were strongest during the first six months of life, with only modest reductions in hospitalizations among children aged six to 23 months.
• Researchers urge larger international studies to evaluate cost-effectiveness and support wider adoption of nirsevimab in infant RSV prevention programs.