OBJECTIVES: Respiratory syncytial virus (RSV) is the leading cause of viral lower respiratory tract illness (LRTI) in young children and is associated with significant morbidity, especially among infants, and important burden on health care systems. Nirsevimab is a monoclonal antibody being developed as a passive immunization for the prevention of medically attended RSV-LRTI (RSV MALRTI).. Understanding its health economic impact under different scenarios is important to determine the optimal implementation strategy to protect infants entering their first RSV season. The objective of this work was to explore the impact of nirsevimab in a French birth cohort compared to current standard of practice.

METHODS: A static Markov model was developed to estimate RSV MALRTIs and costs in a French birth cohort over their first RSV season (October to March). Outpatient inputs were based on literature review and RSV-related hospitalizations came from a retrospective analysis of the French Hospital database (PMSI-MCO), from 2010 to 2018. PMSI provides medico-administrative information on secondary and tertiary care from the public and private sectors.

RESULTS: Under current standard of practice, the model estimated 126,930 RSV MALRTIs over one season with an associated annual economic burden estimated at €105 million. RSV related hospitalizations were equally distributed between infants born within season (WiS) and infants born out of season (OoS). Thirty percent of all RSV MALRTIs were found among WiS births and 70% within OoS births. The most impactful strategy was to immunize all infants (WiS & OoS), regardless of their time of birth, with more than 53% reduction of RSV MALRTIs when a coverage rate of 70% and an efficacy of 70% was assumed, with a 5-month window of protection.

CONCLUSIONS: Nirsevimab is likely to represent value for money if used on a seasonal basis targeted towards protecting all infants during the first year of life within their first RSV season.