OBJECTIVES: Respiratory Syncytial Virus (RSV) is a common cause of lower respiratory tract infection in infants. The purpose of this study is to compare seasonal burden (health events and associated costs) of RSV infections in Japan between standard of practice (SOP: palivizumab for palivizumab-eligible population and no prophylaxis for palivizumab-non-eligible population) and universal immunization with nirsevimab.

METHODS: Economic and clinical impact of universal immunization with nirsevimab for the prophylaxis of RSV medically attended lower respiratory tract infection in Japan was simulated based on a static decision analytic model. One year time horizon was considered. Monthly probabilities of RSV infections were calculated based on the data from the National Institute of Infectious Disease. RSV-related health events: hospitalization, emergency room, outpatient visits, and wheezing – occurrence rates and associated costs were obtained from literature. Efficacy of nirsevimab was derived from a prespecified pooled analysis of clinical trials and of palivizumab from a meta-analysis of randomized controlled trials. The coverage rate of 90% for both strategies was assumed based on real world pediatric vaccine coverage data of National Immunization Program in Japan.

RESULTS: The model estimated a total of 98,108 health events related to RSV infection, including 16,034 hospitalizations, 2,012 ER visits, 67,940 outpatient visits and 12,122 wheezing events under SOP, and a total of 49,247 health events including 8,277 hospitalizations, 1,025 ER visits, 33,688 outpatient visits and 6,257 wheezing events under new prophylaxis with nirsevimab in all infants, resulting in a reduction of 50% of health events. This difference corresponds to an economic saving of JPY 3,277,184,188.

CONCLUSIONS: Immunization of all infants with nirsevimab in Japan substantially reduces the clinical burden of RSV and its associated costs.