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

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. 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. 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%. 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. Respiratory syncytial virus is a common virus that infects the lungs and airways. It is the main cause of serious breathing problems and hospital admissions in babies. These infections also create a heavy workload for pediatric emergency departments. Respiratory syncytial virus infection season may commonly run from October to April. Nirsevimab is a long-acting preventive antibody that helps protect babies from severe respiratory syncytial virus disease. In Italy, healthcare services started giving nirsevimab to babies entering their first respiratory syncytial virus season during the 2024–25 season. We studied the real-world impact of this prevention strategy at Meyer Children’s Hospital in Tuscany, Italy. We compared the 2024–25 respiratory syncytial virus season with the three previous seasons. We analyzed visits to the pediatric emergency department, hospital admissions, and intensive care admissions for lower respiratory tract infections, both when respiratory syncytial virus was confirmed and when the cause of infection was not confirmed. After the introduction of nirsevimab, visits to the emergency department for lower respiratory tract infections dropped by more than two-thirds. Hospital admissions for these infections fell sharply, and intensive care admissions decreased by more than 80%. Confirmed respiratory syncytial virus lower respiratory tract infections almost disappeared. These findings show that protecting eligible babies with nirsevimab greatly reduced serious respiratory infections and eased pressure on hospitals and emergency departments.