Advisers to the U.S. Food and Drug Administration voted Thursday in favor of Pfizer’s
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respiratory syncytial virus vaccine for pregnant people, following extensive debate about its safety.
FDA advisory-committee votes are not binding, but the agency often follows their recommendations. If the FDA ultimately approves the vaccine, called Abrysvo, it would be the first in the U.S. to protect babies against RSV, which is the leading cause of hospitalization for infants under a year old.
RSV is a common respiratory virus that typically causes mild symptoms but can cause severe illness, particularly in infants and older adults. An estimated 50,000 to 80,000 children under 5 years old are hospitalized due to RSV each year in the U.S., according to the Centers for Disease Control and Prevention.
The committee’s vote “is a critical step forward in the scientific community’s long-sought-after goal to help prevent RSV disease in infants during their most vulnerable first six months of life,” Annaliesa Anderson, a senior vice president at Pfizer, said in a statement.
Pfizer is among several pharmaceutical giants that have been racing to develop RSV vaccines. Earlier this month, the FDA approved GSK’s
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Arexvy for prevention of RSV in people 60 and older, making it the first RSV vaccine approved for use in the U.S. Pfizer is also working on a RSV vaccine for older adults, with an FDA approval decision expected later this month.
Nirsevimab, a monoclonal antibody developed by Sanofi
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and AstraZeneca
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and designed to protect infants from RSV, will also be considered by an FDA advisory committee next month.
Almost all children get an RSV infection by the time they are 2 years old, with most having mild, cold-like symptoms, but in some cases the virus causes pneumonia or bronchiolitis, an inflammation of small airways in the lungs, according to the CDC.
The committee voted unanimously that there was enough data to show that the vaccine is effective. But members were split on a second question about safety, with four of the 14 voting members saying there wasn’t adequate data to support the safety of vaccination with Abrysvo during pregnancy.
Several advisory committee members raised questions about the risk of preterm births with the maternal vaccine. Early last year, GSK halted a study of a similar maternal RSV vaccine candidate due to concerns about rates of preterm births in participants receiving the vaccine, committee members noted. “That company abandoned that program, and those decisions are never made lightly,” Dr. Paul Offit, an advisory committee member and director of the vaccine education center at Children’s Hospital of Philadelphia, said during the meeting Thursday.
Pfizer said in documents submitted to FDA that there was no statistically significant difference in preterm births in study participants receiving its maternal vaccine candidate versus a placebo.
“There is certainty that the vaccine works and would keep infants out of the hospital in the United States as soon as this winter if broadly applied,” Dr. William Gruber, a senior vice president at Pfizer, told the committee shortly before the vote. He asked the committee to balance that certainty against the “statistically nonsignificant difference” in prematurity in overall study participants receiving the vaccine, adding that the company is confident that post-approval safety monitoring would quickly resolve the safety concern.
Pfizer
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shares fell 0.7% Thursday, while the S&P 500
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gained 0.9%.
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