This retrospective multicentre study across 19 Italian paediatric units examined RSV-related hospitalisations in children under 18 years over six seasons (January 2019–March 2025), comparing rates before and after regional nirsevimab immunisation rollouts grouped by eligibility criteria (Groups A–G).
10,915 RSV hospitalisations were recorded; in the 2024–2025 season, overall hospitalisations fell 43.6%. Groups with broader eligibility and earlier rollout saw the greatest reductions (Group B ratio 0.28, 95% CI 0.22–0.36; Group A ratio 0.40, 95% CI 0.22–0.74), while narrower or delayed programmes showed modest reductions (ratios 0.58–0.70). One group (G) showed no clear reduction after accounting for baseline instability (ratio 1.84, 95% CI 1.15–2.94).
Observational design prevents causal inference or direct comparison of regional strategies. Group G results were confounded by baseline instability. Group F findings are from a single centre and are only indicative.
Broader nirsevimab eligibility criteria and timely seasonal rollout appear to drive the largest reductions in paediatric RSV hospitalisations. Programmes with narrow eligibility or delayed start showed substantially smaller benefits.
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