The Impact of Nirsevimab on Bronchiolitis‐Related Hospitalizations: A Multicenter Italian Retrospective Comparative Study

ABSTRACT Introduction Bronchiolitis is the leading cause of infant hospitalizations worldwide, primarily driven by respiratory syncytial virus (RSV). Methods This multicenter retrospective comparative study assessed the impact of immunoprophylaxis with nirsevimab against RSV on bronchiolitis‐related hospitalizations in Italy during the 2024–2025 winter season. Results Data from nine Italian hospitals showed a substantial 48% decrease in bronchiolitis admissions compared to the previous season (438 vs. 832 admissions). Among hospitalized infants, only 23% had received immunoprophylaxis. RSV positivity dropped significantly among immunized patients (48%) versus non‐immunized (73%, p < 0.0001), with fewer RSV‐related coinfections. Discussion While indicators of illness severity—such as ICU admission, respiratory support needs, and complications—were generally lower, no statistically significant differences in disease course were observed between immunized and non‐immunized hospitalized infants. A shift in viral epidemiology was noted, with a reduction in RSV dominance and increased detection of rhinovirus and enterovirus, suggesting a pathogen replacement effect. The 2024–2025 season also saw a lower intubation rate (< 0.5%), pointing to an overall milder disease course. Conclusions This study supports the effectiveness of nirsevimab in reducing RSV‐associated hospitalizations and reshaping the virological landscape of bronchiolitis in Italy. Early and widespread implementation of immunoprophylaxis is recommended to maximize public health benefits.