Reduced Emergency Department Visits and Hospitalizations in Infants after Universal Respiratory Syncytial Virus Immunization, Italy, 2024-25

During the 2024-25 winter season, a universal immunization campaign with nirsevimab was implemented in a region of Italy to prevent respiratory syncytial virus (RSV) infection among infants <12 months of age. We assessed its effects using regional syndromic surveillance data on emergency department visits (EDVs) and hospitalizations for lower respiratory tract infections and RSV infections. We estimated expected burden using an interrupted time series analysis, based on historical trends, and observed values with predictions. Children 1-5 years of age, not eligible for immunization, served as a comparison group. Among infants, EDVs for acute lower respiratory tract infections decreased by 42.7% and hospitalizations decreased by 46.5%, whereas EDVs for RSV infection decreased by 49.3% and hospitalizations decreased by 55.0%. No reductions were observed in children 1-5 years of age, confirming ongoing RSV circulation. Our findings support the effectiveness of universal nirsevimab immunization in reducing severe RSV-related outcomes among infants.