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Volume 32, Number 1—January 2026

Research

Reduced Emergency Department Visits and Hospitalizations in Infants after Universal Respiratory Syncytial Virus Immunization, Italy, 2024–25

Simone Villa1Comments to Author , Simona Scarioni1, Enrico Pigozzi, Manuel Maffeo, Mauro Maistrello, Giorgio Bagarella, Francesco Scovenna, Federica Morani, Marlen Romano, Gianvincenzo Zuccotti, Massimo Agosti, Catia Borriello, Elena Pariani, Guido Bertolaso, Luigi Vezzosi, Fausto Baldanti, Mario Melazzini, Elena Azzolini, Gabriele del Castillo2, Danilo Cereda2, and Regional Immunization Council3
Author affiliation: Directorate General for Health, Lombardy Region, Milan, Italy (S. Villa, S. Scarioni, E. Pigozzi, M. Maffeo, M. Maistrello, G. Bagarella, F. Scovenna, F. Morani, C. Borriello, G. Bertolaso, L. Vezzosi, M. Melazzini, G. del Castillo, D. Cereda); University of Milan, Milan (S. Villa, S. Scarioni, E. Pigozzi, F. Scovenna, G. Zuccotti, E. Pariani); Regional Company for Innovation and Purchasing Aria S.p.A., Milan (M. Romano); Buzzi Children’s Hospital, Milan (G. Zuccotti); Hospital “F. Del Ponte,” University of Insubria, Varese, Italy (M. Agosti); Fondazione IRCCS Policlinico San Matteo, Pavia, Italy (F. Baldanti); University of Pavia, Pavia (F. Baldanti); Humanitas University, Pieve Emanuele, Italy (E. Azzolini)

Main Article

Figure 4

Interrupted time series analysis of EDVs (A) and hospitalizations (B) for lower respiratory tract infections among infants <12 months of age in study of reduced EDVs and hospitalizations in infants after universal respiratory syncytial virus immunization, Italy, 2024–25. Numbers are shown for ISO week 35–2021 to ISO week 19–2025. A negative binomial model incorporating a Fourier parameter was trained using historic data before the launch of the universal respiratory syncytial virus immunization program (before October 10, 2024; vertical dashed lines indicate launch date) and was then used to compute predicted values and 95% UIs. Those values are displayed against the observed weekly counts of EDVs and hospital admissions for lower respiratory tract infections. EDV, emergency department visit; UI, uncertainty interval.

Figure 4. Interrupted time series analysis of EDVs (A) and hospitalizations (B) for lower respiratory tract infections among infants <12 months of age in study of reduced EDVs and hospitalizations in infants after universal respiratory syncytial virus immunization, Italy, 2024–25. Numbers are shown for ISO week 35–2021 to ISO week 19–2025. A negative binomial model incorporating a Fourier parameter was trained using historic data before the launch of the universal respiratory syncytial virus immunization program (before October 10, 2024; vertical dashed lines indicate launch date) and was then used to compute predicted values and 95% UIs. Those values are displayed against the observed weekly counts of EDVs and hospital admissions for lower respiratory tract infections. EDV, emergency department visit; UI, uncertainty interval.

Main Article

1These authors contributed equally to this article and share first authorship.

2These authors contributed equally to this article and share last authorship.

3Members of the Regional Immunization Council are listed at the end of this article.

Page created: December 13, 2025
Page updated: January 07, 2026
Page reviewed: January 07, 2026
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