Long-term impact of nirsevimab on prevention of respiratory syncytial virus infection using a real-world global database.
Objective The preventive effect of nirsevimab, a long-acting monoclonal antibody, on infants with respiratory syncytial virus (RSV) infection beyond six months has rarely been evaluated. The objective of this study was to evaluate the preventive effects of nirsevimab beyond 6 months after RSV infection using a global database. Methods This was a multi-centre retrospective study using a global database (TriNetX). The participants were children under 24 months of age who required nucleic acid testing for RSV between July 2023 and June 2025. Children who received the last dose of nirsevimab within 6 months, between 6 and 11 months, and beyond 12 months were compared with those who did not receive any nirsevimab dose by epidemic season after propensity score matching. Results A total of 4627, 861, and 532 children aged <24 months who received nirsevimab within 6 months, between 6 and 11 months, and beyond 12 months before RSV testing, respectively, and 210,626 children who did not receive any nirsevimab were identified. Compared with those who did not receive nirsevimab, the odds ratios (OR) of a positive RSV test result among those who received nirsevimab within 6 months, between 6 and 11 months, and beyond 12 months before testing were 0.49 [95% confidence interval (CI) 0.42, 0.57] (p<0.001), 0.67 [0.48, 0.94] (p<0.020), and 1.21 [0.89, 1.65] (p=0.234) in the last epidemic season, respectively. Conclusion This study indicated that the preventive effect of nirsevimab against RSV infection was maintained for up to 12 months following administration, whereas a preventive effect beyond 12 months was not observed. The results of this study need to be interpreted with caution owing to some important limitations.
Kitano T, Tsuzuki S, Fukuda H et al.