Impact of Nirsevimab on Pediatric RSV-Related Lower Respiratory Tract Infections: A Retrospective Pre–Post Observational Study in Tuscany, Italy

Abstract Introduction Respiratory syncytial virus (RSV) is the leading cause of respiratory infections and hospitalization among infants and a major burden on pediatric emergency department (EDs). Nirsevimab has recently been introduced for universal use in all infants entering their first RSV season. However, real-world data on its public health impact are still limited, particularly regarding attendances at pediatric ED. Methods We conducted a retrospective, observational, pre–post intervention study at the Meyer Children’s Hospital (Tuscany, Italy). The 2024–25 RSV season, when nirsevimab was firstly implemented, was compared with the three preceding seasons. ED attendances, hospitalization, and pediatric intensive care unit (PICU) admissions for lower respiratory tract infections (LRTIs) of any etiology were analyzed. Results During the 2024–25 season, overall ED attendances for LRTIs, regardless of etiology, decreased by 67.3%. Hospital admissions for LRTIs dropped by 64.7%, and PICU admissions by 86.2%. RSV-confirmed LRTIs declined by 96.5%. Conclusions Universal nirsevimab prophylaxis markedly reduced the burden of respiratory infections in eligible infants, leading to a significant reduction in the use of healthcare resources, including ED visits, hospitalization, and PICU admissions.