System Maintenance Notice

Please note that maintenance work is scheduled between 4 AM and 5 AM - CET. During this time, you may experience reduced performance. Thanks for your patience.

Publications

Journal Article Research Support, Non-U.S. Gov't Research Support, N.I.H., Extramural Epublish 55 citations

PubMed: 40063022 DOI: 10.1001/jamanetworkopen.2025.0380

Estimated Effectiveness of Nirsevimab Against Respiratory Syncytial Virus.

JAMA Netw Open 8(3):e250380

Authors: Hanmeng Xu, Camila Aparicio, Aanchal Wats, Barbara L Araujo, Virginia E Pitzer, Joshua L Warren, Eugene D Shapiro, Linda M Niccolai, Daniel M Weinberger, Carlos R Oliveira

Affiliations

  • Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut.
  • Department of Pediatrics, Section of Infectious Diseases and Global Health, Yale School of Medicine, New Haven, Connecticut.
  • Department of Biostatistics, Yale School of Public Health, New Haven, Connecticut.
  • Department of Biostatistics, Section of Health Informatics, Yale School of Public Health, New Haven, Connecticut.
  • Department of Biomedical Informatics and Data Science, Yale School of Medicine, New Haven, Connecticut.

Abstract

IMPORTANCE

Nirsevimab, a long-acting monoclonal antibody, demonstrated efficacy against respiratory syncytial virus (RSV)-associated lower respiratory tract infections (LRTI) in clinical trials. Postlicensure monitoring is essential to confirm these benefits in clinical settings.

OBJECTIVE

To estimate the effectiveness of nirsevimab against medically attended RSV infections in infants and to assess how effectiveness varies by disease severity, dosage, and time since immunization.

DESIGN, SETTING, AND PARTICIPANTS

This test-negative case-control study utilized inpatient, outpatient, and emergency department data from the Yale New Haven Health System. Nirsevimab-eligible infants who were tested for RSV using polymerase chain reaction between October 1, 2023, and May 9, 2024, were included. Infants with RSV-positive results were cases and infants with RSV-negative results were controls.

EXPOSURE

Nirsevimab immunization, verified through state immunization registries.

MAIN OUTCOMES AND MEASURES

Effectiveness was estimated using multivariable logistic regression, adjusting for age, calendar month, and potential confounders. Separate models examined estimated effectiveness by clinical setting, dosage, time since immunization, and severity (defined as needing high-flow oxygen or intensive care unit admission). Broader outcomes were also analyzed, including all-cause LRTI and all-cause LRTI-associated hospitalization.

RESULTS

The analytic sample included 3090 infants (1722 male [57.3%]; median [IQR] age at testing, 6.7 [3.6-9.7] months), with 680 (22.0%) RSV-positive cases and 2410 (78.0%) RSV-negative controls. Nirsevimab uptake was 10.7% (330 patients), with 21 RSV-positive cases and 309 RSV-negative controls immunized. Adjusted effectiveness was 68.4% (95% CI, 50.3%-80.8%) against medically attended RSV infection, 61.6% (95% CI, 35.6%-78.6%) against outpatient visits, and 80.5% (95% CI, 52.0%-93.5%) against hospitalizations. The highest estimated effectiveness (84.6%; 95% CI, 58.7%-95.6%) was observed against severe RSV disease. Although estimated effectiveness against RSV infections declined from 79.3% (95% CI, 63.4%-90.6%) at 2 weeks postimmunization to 54.8% (95% CI, 16.3%-74.7%) at 14 weeks postimmunization, it remained significant. Estimated effectiveness did not vary substantially by dosage. During peak RSV season, nirsevimab appeared effective against all-cause LRTI (49.4%; 95% CI, 10.7%-72.9%) and all-cause LRTI-associated hospitalizations (79.1%; 95% CI, 27.6%-94.9%). From February to May 2024, when most LRTIs were caused by other viruses, its estimated effectiveness against these broader outcomes was negligible.

CONCLUSIONS AND RELEVANCE

In this case-control study, nirsevimab provided substantial protection against RSV-associated outcomes. These findings support its continued use and provide evidence that may help boost public confidence in the immunization program.

MeSH

Respiratory Syncytial Viruses, Immunization, Hospitalization, Case-Control Studies, Clinical Medicine, Viruses, Outpatients, Infections, Infant

Cited by