Evaluating the Effectiveness of Nirsevimab in Reducing Pediatric RSV Hospitalizations in Spain

Background and objective Respiratory syncytial virus (RSV) is a major cause of hospitalization in infants. Nirsevimab has demonstrated to be a promise tool for preventing severe RSV disease. Although clinical trials have demonstrated the efficacy of Nirsevimab in preventing severe RSV disease, evidence regarding its performance in real-world clinical settings is still limited due to its recent introduction. This study aims to fill this knowledge gap by evaluating the impact of Nirsevimab in a cohort of infants and determining its effectiveness in reducing the burden of RSV disease. Material and Methods Retrospective study of RSV hospitalizations in children under six months of age, between October 1st and March 31st, across four seasons: pre-COVID (2018-2019), COVID (2019-2020), post-COVID pre-Nirsevimab (2022-2023), and Nirsevimab season (2023-2024). Results Nirsevimab has demonstrated significant efficacy in reducing RSV-related hospitalizations in infants under six months of age. During the 2023/24 season, following the introduction of Nirsevimab, there was a substantial reduction in RSV-related lower respiratory tract infection (LRTI) hospitalizations. Among infants under 3 months of age, hospitalizations decreased by 79.3% (IRR: 0.21, 95% CI: 0.12-0.34). In infants aged 3 to 6 months, there was a 66.9% reduction (IRR: 0.33, 95% CI: 0.15-0.64). Additionally, Nirsevimab decreased the severity of RSV cases with LRTI who required support of equipment for sanitary use further reducing overall healthcare burden. Conclusion These results underscore Nirsevimab's vital role in preventing severe RSV infections and hospitalizations, especially among the most vulnerable infants, positioning it as a critical advancement in pediatric respiratory care.