RSV Efficacy vs. Real-World Effectiveness: What the Data Reveal

This episode provides a clear-eyed analysis of what RSV preventive strategies can and cannot accomplish, drawing on both clinical trial efficacy and post-licensure real-world effectiveness data. Dr. Creech opens by defining realistic endpoints: total prevention of RSV infection is not achievable, given how well-adapted this virus is to human hosts. The true measure of success is reducing severe lower respiratory tract disease and hospitalizations.

With that frame, the results are compelling. Real-world data indicate these preventive strategies reduce RSV hospitalizations by 60% to 85%, depending on the population and timing of administration. Children who are hospitalized despite receiving prophylaxis tend to have shorter stays, lower ICU admission rates, and less need for supplemental oxygen. For medically attended lower respiratory tract infections, effectiveness ranges from 60% to 75%. These outcomes hold across subgroups, though there are nuances in populations with prematurity or underlying cardiopulmonary disease.

Dr. Creech also emphasizes safety: side effect profiles for both maternal vaccination and monoclonal antibodies are remarkably benign. Injection site reactions occur in a minority of infants; fever is rare. There is no meaningful anaphylaxis risk, minimal immunogenicity, and no induction of allergy. Dr. Creech articulates the overarching message that both maternal immunization and monoclonal antibodies work, are safe, and that any apparent nuances between them in clinical trial data should not be overinterpreted until both are studied extensively in real-world, diverse populations.

In the next episode, "RSV Post-Authorization Data and Second-Season Protection: Emerging Evidence," Dr. Simões reviews real-world effectiveness findings from the UK, France, and Argentina, and discusses what is known about extending protection into a second RSV season.