by Justin Jackson , Medical Xpress

Transmission electron micrograph of RSV. Credit: CDC/ Dr. Erskine Palmer / Public Domain

Research led by the CDC and conducted at seven academic pediatric medical centers in the United States finds nirsevimab (sold as Beyfortus) highly effective in reducing respiratory syncytial virus (RSV) related hospitalization in children under 5 years old.

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RSV is a common respiratory virus that causes mild, cold-like symptoms in healthy adults. Infants are more likely to develop severe RSV, especially those younger than 12 months.

RSV is the leading cause of hospitalization in U.S. infants. Circulation typically peaks between December and February, leading to 50,000 to 80,000 hospitalizations, mostly of infants in the first months of life. Nirsevimab is an FDA approved long-acting monoclonal antibody designed to prevent RSV lower respiratory tract illness in infants under 8 months.

In 2023, health authorities approved and recommended nirsevimab for all infants entering their first RSV season and a maternal RSV vaccine during late pregnancy to protect young infants.

In a prospective, population-based surveillance study, “Respiratory Syncytial Virus Disease Burden and Nirsevimab Effectiveness in Young Children From 2023–2024,” published in JAMA Pediatrics, the research team evaluated the effectiveness of the new interventions.

28,689 children under five years old who sought medical care for acute respiratory illness across seven U.S. pediatric centers were included in the study. Approximately a quarter of them tested positive for RSV.

Nirsevimab demonstrated 89% effectiveness against medically attended RSV-associated acute respiratory illness and 93% effectiveness against RSV-associated hospitalizations, although only 442 infants received the treatment.

RSV circulation typically follows a seasonal pattern, peaking nationally from December through February, but the COVID-19 pandemic disrupted these patterns in recent years. During the 2023–2024 RSV season, disease burden in children younger than 5 years was substantial and did not differ notably from pre-pandemic seasons.

Data showed newly recommended preventive measures, including nirsevimab, displayed effectiveness against medically attended RSV-associated acute respiratory illness, but that adherence to the new recommendations was limited. Maternal vaccine use was so low that outcomes could not be assessed by the study.

The effectiveness of nirsevimab, along with the unmet need of infants facing RSV for the first time, suggests a substantial public health impact could be achieved with increased prevention coverage in future seasons.

More information: Heidi L. Moline et al, Respiratory Syncytial Virus Disease Burden and Nirsevimab Effectiveness in Young Children From 2023-2024, JAMA Pediatrics (2024). DOI: 10.1001/jamapediatrics.2024.5572

Journal information:JAMA Pediatrics

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