Monoclonal antibody medication nirsevimab reduced risk of severe respiratory illness in babies
Babies who received nirsevimab, a monoclonal antibody preventive medication, were 87% less likely to have severe illness from respiratory syncytial virus (RSV) than those who did not receive nirsevimab, according to a Kaiser Permanente study published in the journal Pediatrics.
The researchers wanted to track how well the medication protected babies against RSV with lower respiratory tract disease (LRTD) — severe disease such as bronchiolitis or pneumonia — or kept them from being infected with RSV.
The children who received nirsevimab were 87% less likely to have RSV-related LRTD, 98% less likely to be hospitalized with RSV, and 71% less likely to have an RSV infection. “We found nirsevimab offered strong protection against RSV-related complications and severe cases,” said lead author Amber Hsiao, PhD, MPH, a project manager for the Kaiser Permanente Division of Research.
The study included 31,900 healthy full-term infants without high-risk conditions born to members of Kaiser Permanente Northern California. Of these, 49% received nirsevimab, most of whom received it by 6 months of age.
Of all the infants, there were 35 RSV LRTD cases among the immunized babies and 462 among the non-immunized babies. The analysis found that among babies who became ill with RSV, those treated had fewer medical encounters and were less likely to be hospitalized.
The results were consistent with other real-world research on nirsevimab effectiveness during the 2023-24 season, said senior author Nicola Klein, MD, PhD. This study added evidence on effectiveness against laboratory-confirmed RSV infection. “There have not been a lot of studies that also evaluated how well nirsevimab protected against potentially milder cases of RSV without complications who were seen only in the outpatient setting,” she said.
RSV is the leading cause of lower respiratory tract disease in infants and young children. RSV with LRTD is the most common cause of hospitalization in children under 1 year old.
Nirsevimab was licensed in 2023 and was recommended by federal public health officials to be administered in all healthy infants under 8 months of age entering their first RSV season and to high-risk infants aged 8 to 15 months in their first and second RSV seasons.
The study was funded by Sanofi.
Additional co-authors were John Hansen, MPH, Julius Timbol, MS, and Ousseny Zerbo, PhD, of the Vaccine Study Center (VSC); Bruce Fireman, MA, formerly of the VSC; Karine Mari, MSc, of Sanofi Pasteur; and Christopher Rizzo, MD, William La Via, MD, and Ruvim Izikson, MD, MPH, of Sanofi Vaccines.
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About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. KPDOR seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 720-plus staff, including 73 research and staff scientists, are working on nearly 630 epidemiological and health services research projects. For more information, visit divisionofresearch.kp.org or follow us @KPDOR.
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