Severe Pediatric Respiratory Syncytial Virus Infections Occurring in the Era of Antiviral Prophylaxis

Hospitalization for RSV lower respiratory tract infections (LRTI) still occurs, including in infants having received nirsevimab/clesrovimab or born to mothers vaccinated with Abrysvo. We hypothesize that pediatric patients hospitalized for RSV LRTIs occurring in the era of large use of prophylaxis, could be, at least in part, explained by virological factors (emergence/selection of variants with decreased susceptibility to prophylaxis) and/or immunological factors (inherited immune deficiency, presence of auto-antibodies neutralizing anti-viral cytokines such as type I interferons, impaired mucosal responses or mucosal pharmacokinetics issues inducing low levels of local concentrations of nirsevimab/clesrovimab).