Public health impact of nirsevimab and reduction of RSV hospitalisation in all infants: early real-world data from Tuscany (Italy) in the 2024–25 RSV season

Real-world evidence on the public health impact of nirsevimab across a full RSV season in Italy is currently lacking, particularly with respect to hospitalisations and admissions to paediatric intensive care units (PICU), and only limited data are available worldwide. This study aimed to evaluate, in a real-world setting, the public health impact of nirsevimab on RSV-related hospitalisations and PICU admissions in Tuscany. This observational retrospective study included all children under one year of age experiencing their first RSV season, i.e., those born between April and March of the 2021-22, 2022-23, 2023-24, and 2024-25 seasons, who were hospitalised at the Meyer Children's Hospital, a tertiary regional paediatric hospital in Tuscany, for respiratory symptoms with RSV confirmed via real-time PCR testing. Starting November 1st 2024, Nirsevimab was offered to all infants born between 1 April, 2024, and 31 March, 2025. The percentage reduction in RSV-related hospitalisations was calculated by comparing the number of hospitalisations observed in 2024/25 with the mean number recorded across the three preceding RSV seasons. Immunization coverage reached around 90%. During the 2024-2025 RSV season, RSV-related. hospitalisations decreased by 82.1% among infants eligible for immunization, by 83.2% among those born during the RSV season, and by 81.5% among those born before the season. PICU admissions decreased by 85.2%, 84.0%, and 86.8%, respectively, in the same groups. High coverage of nirsevimab immunization substantially reduced RSV-related hospitalisations among infants in Tuscany during the 2024-2025 season. The consistent benefits observed across both in-season and out-of-season birth cohorts support a universal immunization program for all infants, including those born from April onward, in Italy. What is Known: • RSV is the leading cause of infant hospitalisations for lower respiratory tract infections, especially in those ≤12 months. Real-world data on season-wide nirsevimab public health impact in Italy were lacking.. What is New: • Universal nirsevimab immunisation in Tuscany led to an 82.1% reduction in RSV-related hospitalisations and 85.2% in PICU admissions in infants eligible for immunization. Findings support universal over selective immunisation to protect all infants entering their first RSV season.