What does this research mean for the field?

Nirsevimab reduced bronchiolitis-related hospitalizations by 48% compared to the previous season, with significant decreases in RSV positivity among immunized patients. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.SUPPORTS_CONSENSUS.

What question did this study set out to answer?

This research aims to assess the effectiveness of nirsevimab in reducing bronchiolitis-related hospitalizations due to RSV.

February 11, 2026Open Access

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

Key Result

Nirsevimab immunoprophylaxis reduced bronchiolitis hospitalizations by 48% and RSV positivity from 73% to 48% among infants in Italy's 2024-2025 season.

Key Points

This research aims to assess the effectiveness of nirsevimab in reducing bronchiolitis-related hospitalizations due to RSV.
Multicenter retrospective comparative study
Data collection from nine Italian hospitals
Comparison of hospital admissions for bronchiolitis between seasons
Analysis of RSV positivity among immunized and non-immunized infants
48% decrease in bronchiolitis admissions compared to the previous season
Only 23% of hospitalized infants received nirsevimab
RSV positivity in immunized patients: 48% vs non-immunized: 73% (p < 0.0001)
Lower ICU admission and intubation rates, indicating milder disease course
Shift in viral epidemiology with reduced RSV dominance and increased rhinovirus and enterovirus detections

Structured PICO

Does nirsevimab reduce bronchiolitis-related hospitalizations in infants?

Population

Infants hospitalized for bronchiolitis in Italy during the 2024-2025 winter season

Intervention

Immunoprophylaxis with nirsevimab against RSV

Comparator

Previous season (2023-2024) without nirsevimab, and non-immunized infants in the same season

Outcome

Bronchiolitis-related hospitalizationshard clinical

Nirsevimab immunoprophylaxis substantially reduces RSV-associated hospitalizations and alters the virological landscape of bronchiolitis in infants.

Main Result

Absolute Event Rate: 0% vs 0%

Abstract

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.