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Updated: Jan 11, 2026
An Improved and High Throughput Respiratory Syncytial Virus RSV Micro-neutralization Assay
Published on: January 26, 2019
Long-term impact of nirsevimab on prevention of respiratory syncytial virus infection using a real-world global
Taito Kitano1, Shinya Tsuzuki2, Haruhisa Fukuda3
1Department of Pediatrics, Nara Prefecture General Medical Center, Nara, Japan; Clinical Research Center, Nara Prefecture General Medical Center, Nara, Japan; AMR Clinical Reference Center, Japan Institute for Health Security, Tokyo, Japan; Disease Control and Prevention Center, Japan Institute for Health Security, Tokyo, Japan.
Insights
Nirsevimab, a long-acting antibody, effectively prevents respiratory syncytial virus (RSV) infection in infants for up to 12 months. However, its preventive effect diminishes beyond 12 months, indicating a limited duration of protection against RSV.
Area of Science:
- Pediatrics
- Infectious Diseases
- Immunology
Background:
- Respiratory syncytial virus (RSV) is a major cause of infant respiratory illness.
- Nirsevimab, a long-acting monoclonal antibody, offers passive immunization against RSV.
- The duration of nirsevimab's preventive effect beyond six months requires further evaluation.
Purpose of the Study:
- To assess the preventive efficacy of nirsevimab against RSV infection in infants for longer than six months.
- To analyze nirsevimab's effectiveness using a global health database.
Main Methods:
- Retrospective, multi-center study utilizing the TriNetX global database.
- Inclusion of children under 24 months requiring RSV nucleic acid testing (July 2023-June 2025).
- Comparison of nirsevimab recipients (dosed within 6 months, 6-11 months, >12 months) versus non-recipients using propensity score matching.
Main Results:
- Nirsevimab administration within 6 months showed a significant reduction in positive RSV test results (OR 0.49, p<0.001).
- Protection was observed between 6-11 months (OR 0.67, p<0.020), but not beyond 12 months (OR 1.21, p=0.234).
- A total of 4627, 861, and 532 children received nirsevimab in the respective timeframes, compared to 210,626 controls.
Conclusions:
- Nirsevimab provides sustained protection against RSV infection for up to 12 months post-administration.
- Preventive effects of nirsevimab were not observed beyond 12 months.
- Study findings should be interpreted cautiously due to inherent limitations.
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.
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