How a major discovery can become a public health failure when used subotptimally: lessons from early nirsevimab implementation.

BACKGROUND: In this Debate, based on our clinical data from the "pre-nirsevimab" and "first year of nirsevimab implementation" bronchiolitis seasons, we challenge the validity of policy decisions that led to partial immunization coverage of eligible newborns and infants during the 2024-25 season in Italy. MAIN BODY: Starting with a pre-nirsevimab prospective cohort of 780 newborns, we documented that 84 (9.2%) were diagnosed with acute bronchiolitis (45 of them (5.8% of the cohort) were RSV positive. 44 patients (5.6%) were hospitalized due to bronchiolitis, of which 7 (0.9%) patients were admitted to the Pediatric Intensive Care Unit. Among hospitalized, 31 infants (70%) had RSV infection. Secondly, we evaluated the impact on bronchiolitis admissions during the first year of nirsevimab use in our region, showing a negligible effect on the most severe cases, probably due to the fact that a low coverage will risk to miss the relatively small number of infants (about 10%) that will develop RSV bronchiolitis in the first year of life. These findings inspired our clinical insights and reflections arguing that without a long-term, cost-conscious approach to implementation, even major scientific breakthroughs like nirsevimab risk becoming public health failures. CONCLUSIONS: Our clinical insights and reflections aim to inspire deeper engagement among policymakers, health agencies, and clinicians to better adapt and integrate RSV preventive strategies-maximizing benefit not only for susceptible infants, but for society at large. In a world of finite healthcare resources, optimizing both the reach and the value of such essential interventions is imperative, given the multitude and diversity of health needs our society is facing.