Federica Attaianese, Sandra Trapani, Ilaria Alberti, Maurizio Aricò, Marina Attanasi, Giulia Bertolucci, Silvia Bressan, Désirée Caselli, Veronica Casotto, Salvatore Cazzato, Francesco Chiarelli, Enrico Felici, Anna Frusciante, Maria Antonia Galeone, Silvia Garazzino, Antonietta Giannattasio, Eloisa Gitto, Antonio Guerriero, Fiorentina Guida, Giovanna Iudica, Marcello Lanari, Claudia Mandato, Alice Manzini, Gaia Martelli, Gregorio Paolo Milani, Maria Moriondo, Lucia Dora Notarangelo, Felice Nunziata, Roberta Pellegrino, Diego Peroni, Emanuela Piccotti, Eduardo Ponticiello, Silvia Ricci, Immacolata Rulli, Fabio Savoia, Erika Silvestro, Antonella Sisto, Federica Soro, Stefania Tonetto, Alessandro Zago, Carlo Dani, Chiara Azzari, Giuseppe Indolfi
These population-level study describe a temporal association between the 2024-2025 nirsevimab rollout and reduced RSV hospitalisations, particularly with broader eligibility and timely rollout. The study design cannot establish causation or compare the effectiveness of regional strategies.
OBJECTIVES: To describe paediatric RSV-hospitalisation trends over six seasons and changes following regional nirsevimab strategies in Italy.
METHODS: A Retrospective study across 19 Italian paediatric units was conducted analysing RSV-related hospitalisations in patients aged <18 years from January 2019 to March 2025. Centres were grouped by regional nirsevimab eligibility criteria (Groups A-G). Group-level ratios of 2024-2025 to pre-immunisation hospitalisations were estimated with a negative-binomial model. Influenza was analysed as a negative control RESULTS: 10,915 RSV hospitalisations were recorded. In 2024-2025 RSV season, hospitalisations decreased 43.6% overall. The largest reductions were in groups with broader eligibility and earlier initiation (Group B: ratio 0.28, 95% CI 0.22-0.36; Group A: 0.40, 95% CI 0.22-0.74) and Group F (0.24; single centre, interval indicative). Groups C, D, and E showed more modest reductions (ratios 0.58-0.70), with Group C spanning unity (0.58, 95% CI 0.27-1.25). Group G showed no clear change once baseline instability was accounted for (1.84, 95% CI 1.15-2.94).
CONCLUSIONS: These population-level study describe a temporal association between the 2024-2025 nirsevimab rollout and reduced RSV hospitalisations, particularly with broader eligibility and timely rollout. The study design cannot establish causation or compare the effectiveness of regional strategies.