Health economic evaluation of implementing a universal immunization program with nirsevimab compared to standard of care for the prevention of respiratory syncytial virus disease in Canadian infants.

Respiratory syncytial virus (RSV) is a highly contagious pathogen and a leading cause of severe lower respiratory tract illness (LRTI) in infants and young children, irrespective of risk factors. Nirsevimab, an extended half-life monoclonal antibody, was approved in Canada in 2023 as a passive immunizing agent for the prevention of RSV LRTI. This study evaluated the optimal price per dose (PPD) at commonly accepted willingness-to-pay (WTP) thresholds among Canadian infants compared to the current standard of care (i.e. palivizumab for preterm infants and those with specific medical conditions). A static decision tree model was developed to assess the impact of nirsevimab on RSV-related health and economic outcomes among Canadian infants - including outpatient physician and emergency department visits, inpatient hospitalizations including intensive care unit (ICU) admissions and mechanical ventilation, and the associated healthcare costs of these outcomes. The model utilized Canadian epidemiological and cost inputs where possible, adopting a societal perspective. Compared to the standard of care, nirsevimab was expected to prevent 47,609 RSV-related health events, including 2,296 hospitalizations and a reduction of approximately $45 million in direct healthcare costs. At a WTP threshold of $50,000 per quality-adjusted life-year (QALY), the estimated base case PPD was $536, based on average cost assumptions across several costing scenarios. These findings suggest that universal immunization with nirsevimab could significantly reduce the health and economic burden of RSV among Canadian Infants.