Safety of nirsevimab in children aged 0–24 months: Analysis based on EudraVigilance data (2023–2025)

Respiratory syncytial virus (RSV) is a cause of severe lower respiratory tract infections in infants, and it is associated with substantial morbidity, including hospitalization and death. After European Medicine Agency approval of nirsevimab, a monoclonal antibody against RSV, immunization campaigns have been implemented in several European Union countries for administration to children as preventive intervention against severe RSV disease during RSV epidemic season. Monitoring its safety in routine healthcare practice is also important. We described suspected adverse drug reactions (ADRs) following nirsevimab administration in children aged 0-24 months, reported in the EudraVigilance system between 2023 and 2025. There were 1,923 ADRs, corresponding to 808 cases. By System Organ Class, ADRs mainly included general disorders and administration site conditions, which include nonspecific systemic manifestations and administration-site reactions that cannot be readily assigned to a single organ system (28.4%), infections and infestations (23.3%), respiratory, thoracic, and mediastinal disorders (12.2%); by Preferred Terms most frequent were drug ineffective (12.6%), and RSV bronchiolitis (9.6%). In addition, pyrexia, rash, and injection site reactions were also common. This study offered systematic characterization of ADRs following administration of nirsevimab. It found that the reported ADRs are consistent with the safety results from pre- and real-world safety studies. Our study can support the continue monitoring of the real-world safety and guide the planning of analytical observational studies on the safety profile of nirsevimab.