Acute viral bronchiolitis before and after implementation of

Summary: Background: Acute viral bronchiolitis is the leading cause of hospitalisation in the first year of life, with Respiratory Syncytial Virus (RSV) accounting for more than 60% of cases. A long-acting monoclonal antibody ( nirsevimab ) has been introduced for infants entering their first epidemic season. 2024–2025 season was the first with nirsevimab availability in Italy. We assessed its impact on bronchiolitis-related utilisation and clinical and virological characteristics of hospitalised infants.