Studies find RSV protection for infants cuts hospitalizations
As the number of respiratory syncytial virus (RSV) infections rises nationwide, attention is turning to two recent studies that found protecting babies against the disease — by vaccinating pregnant mothers or giving newborns antibodies — prevented hospitalizations in infants. Treating newborns directly was more effective than maternal vaccination.
One study that included just over 5,000 U.S. children found that maternal RSV vaccination reduced RSV-related medical visits by 64% and hospitalizations by 70%, while treating infants with the antibody shot nirsevimab reduced hospitalizations by 81%. Overall, hospitalization rates during the 2024-2025 RSV season were reduced by 41% to 51% among infants younger than 11 months, compared with 2017-2020 rates, researchers estimated.
The second study, which included more than 42,000 French newborns, found that babies given nirsevimab were 25% less likely to be hospitalized than babies born to mothers who were vaccinated against RSV.
However, senior Food and Drug Administration (FDA) officials recently questioned the safety of some treatments and reportedly opened investigations into them. The agency has not released any additional information and thus far has not altered its prior recommendations around vaccination.
What is RSV and how is it treated?
RSV is a common seasonal virus that causes respiratory infections. It starts spreading around the same time as the flu, and case counts peak in December or January.
For most people, RSV infections cause mild symptoms that mimic a common cold. However, infants and the elderly are at a heightened risk for severe illness. Each year, between 190,000 and 350,000 people in the U.S. are hospitalized with RSV, and between 10,000 to 23,000 people die from their infections.
Since 2023, the FDA has approved three RSV vaccines: GlaxoSmithKline’s Arexvy, Pfizer’s Abrysvo, and Moderna’s mResvia. Pfizer’s vaccine is the only one approved for use in pregnant women. The FDA also approved two antibody treatments — Sanofi’s nirsevimab and Merck’s Enflonsia — for infants born during or just before RSV season.
Vaccine safety concerns
Initial studies reported that the RSV vaccines were safe and effective at reducing severe RSV illness and death. However, in October 2024, the Advisory Committee on Immunization Practices, a group of physicians and public health officials that develops guidance about the use of vaccines, reviewed post-licensure safety data for the GlaxoSmithKline and Pfizer’s RSV vaccines. The panel concluded that the two vaccines were associated with an increased risk of developing Guillain-Barré syndrome — a rare autoimmune disorder in which the immune system attacks the nervous system.
Across both vaccines, the FDA estimated the risk of developing the disorder was about 10 excess cases per 1 million vaccinated adults 60 or older. In January 2025, the FDA required both companies to add warning labels to the vaccines.
Last year, as early as June, several FDA officials further questioned the safety of RSV treatments and initiated an investigation, a Health and Human Services Department spokesperson told Reuters. Officials from the FDA’s Center for Drug Evaluation and Research reportedly held a phone call with three pharmaceutical companies who manufacture RSV vaccines and treatments, warning them to expect further safety questions from the agency.
U.S. health officials have typically recommended that older adults, pregnant women and infants receive the RSV vaccine or antibody treatment.
To date, the Department of Health and Human Services has not changed its recommendations. Straight Arrow News reached out to the FDA for further information about its investigation.
“At the FDA we are continuously reviewing and analyzing data to ensure we are maintaining our safety and efficacy standards. The agency cannot comment on potential or future regulatory decisions,” a spokesperson said.
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Ella Rae Greene, Editor In Chief
