The Impact of Nirsevimab Prophylaxis on RSV Hospitalizations: A Real-World Cost-Benefit Analysis in Tuscany, Italy

Vieri Lastrucci¹Martina Pacifici²Giorgia Alderotti¹Monia Puglia²Elettra Berti³Federica Barbati^4*Lorenzo Lodi^5,6Silvia Boscia⁶Francesco Nieddu⁶Giuseppe Indolfi^5,7Diego G Peroni⁸Marco Martini⁹Chiara Azzari^10,6Fabio Voller²Maria Moriondo⁶Silvia Ricci^10,6

• ¹Epidemiology Unit, Meyer Children's Hospital IRCCS, Florence, Tuscany, Italy
• ²Epidemiologic Observatory, Regional Healthcare Agency of Tuscany, Firenze, Italy, Florence, Italy
• ³Neonatal Intensive Care Unit, Meyer Children’s Hospital IRCCS, Firenze, Italy, Florence, Italy
• ⁴Pediatrics and Neonatology Unit, Santo Stefano Hospital, USL Toscana Centro, Prato, Italy, Prato, Italy
• ⁵Department of Neurofarba, University of Florence, Florence, Italy, Florence, Italy
• ⁶Immunology Unit, Department of Pediatrics, Meyer Children's Hospital IRCCS, Florence, Tuscany, Italy
• ⁷Liver Unit, Department of Pediatrics, Meyer CHildren's Hospital IRCCS, Florence, Tuscany, Italy
• ⁸Pediatric Clinic, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy, pisa, Italy
• ⁹Pediatric Unit, San Donato Hospital, Arezzo, Italy, arezzo, Italy
• ¹⁰Department of Health Sciences, University of Florence, Florence, Tuscany, Italy

Background: Respiratory Syncytial Virus (RSV) is the leading cause of hospitalizations in infants. The approval of nirsevimab, a long-acting monoclonal antibody, has extended the potential for RSV prophylaxis to all infants. This study assesses the cost-benefit of various Nirsevimab prophylaxis strategies for infants during their first RSV season in preventing RSV-associated hospitalization in the Tuscany region, Italy.Methods: The analysis was conducted from the perspective of the healthcare payor. Real-world data from the Tuscany birth cohort (N=21,017) experiencing their first RSV season in the 2023/2024 season were used to calculate the net benefit and benefit cost ratio (BCR) of three possible nirsevimab prophylaxis strategies compared with prophylaxis practices at the time of the study, which includes the use of palivizumab in eligible infants. RSV-associated hospitalizations and severe hospitalizations were considered as health outcomes. Sensitivity analyses were performed to identify influential variables. Results: Under prophylaxis practices at the time of the study, there were a total of 663 hospitalizations associated with RSV, including 102 severe cases, representing €5,247,645 in costs. An extended prophylaxis strategy with nirsevimab, including all infants born both before and during the RSV season, resulted in the highest number of hospitalizations avoided (378), with a BCR close to break-even (0.96). A seasonal-only strategy targeting infants born during the season prevented the fewest hospitalizations (252), showing a positive BCR of 1.15. Finally, a seasonal strategy with targeted catch-up, including also preterm infants born before the season, yielded the highest cost-benefit ratio (1.56), preventing 270 hospitalizations.Conclusions: Universal prophylaxis strategies with nirsevimab, targeting all infants during their first RSV epidemic season, substantially reduce hospitalization burdens without increasing economic pressure on the healthcare system. Although alternative strategies are more cost-effective, they prevent fewer hospitalizations, emphasizing the public health value of broader prophylaxis approaches.