RSV Post-Authorization Data and Second-Season Protection: Emerging Evidence

In this episode, Dr. Simões reviews the post-licensure landscape, highlighting data from real-world effectiveness studies now emerging from multiple countries. Initial real-world data for one monoclonal antibody came from the UK and France, including pragmatic trial evidence. Argentina provided complementary data on maternal immunization, having implemented it as an exclusive strategy — while the UK used monoclonal antibody prophylaxis exclusively and France deployed both approaches, offering a natural comparison. A notable French population-based study published in JAMA found a statistically significant difference in effectiveness between the two strategies; however, Dr. Simões cautions that the overlapping 95% confidence intervals suggest the clinical difference may not be meaningful. Importantly, real-world effectiveness broadly mirrors the results seen in randomized controlled trials — a reassuring finding that validates these interventions at scale. Dr. Simões highlights that real-world studies are beginning to capture outcomes not measured in trials, including effects on ICU admissions, otitis media, and all-cause respiratory hospitalizations. For second-season protection, early data with nirsevimab suggests continued benefit, though the full picture is still emerging. Evidence for clesrovimab's second-season efficacy has been presented at scientific meetings and reviewed by the FDA but has not yet received formal approval in the U.S. for this indication. The panel agrees that as additional seasons accumulate data, the understanding of sustained protection will sharpen considerably. In the next episode, "RSV Prevention in Practice: Eliminating Gaps in Immunization Coverage," Dr. Creech and Dr. Tan review the common gaps in RSV prophylaxis delivery and how pediatric practices can build systems to ensure every eligible infant is protected.