Making regional comparisons policy-ready: clarified, standardised methods and region-wide RSV hospital discharge estimates from Emilia-Romagna, Italy.

Respiratory syncytial virus (RSV) prophylaxis with nirsevimab was introduced in Italy from the 2024–2025 epidemic season. The preprint “Impact of Regional heterogeneity of RSV infection prophylaxis on bronchiolitis in Italy” provides timely information for clinicians and health-system planners; however, several methodological specifications require clarification to ensure reproducibility and valid cross-regional comparability, particularly for the Emilia-Romagna Region. In Emilia-Romagna, programme choices were supported by a retrospective analysis of routinely collected hospital discharge and birth registry data (2015–2023), documenting that most of the RSV-associated hospital-admission burden is concentrated in infancy and follows a marked seasonal pattern, with severe outcomes largely confined to the first year of life. This evidence informed a risk-stratified approach during the initial roll-out. Using region-wide hospital discharge records from all Emilia-Romagna hospitals, we observed larger reductions between October 2023–March 2024 and October 2024–March 2025 than those presented as “regional” estimates in the preprint: total hospitalisations decreased from 1384 to 607 (−56.1%) among children aged < 14 years and from 1131 to 364 (−67.8%) among infants aged < 1 year; paediatric intensive care unit admissions decreased from 136 to 32 (−76.5%) and from 126 to 23 (−81.7%), respectively. To maximise the policy value of cross-regional comparisons and to support a more uniform, evidence-based national strategy in future seasons, key methods should be reported in a clear and standardised way.