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An advisory panel for the Food and Drug Administration voted Thursday to approve a vaccine by Pfizer to prevent a severe respiratory virus that poses a deadly threat to infants.
The vaccine would be the first to protect babies from respiratory syncytial virus, or RSV, which is the cause of many babies being hospitalized each year and killing several hundred under the age of 5.
Fourteen of the agency’s advisers unanimously agree that the vaccine is effective, and the FDA usually follows its advisory panel’s recommendations.
Ten of the 14 agreed that the vaccine is safe, with some raising concerns about increased rates — not all statistically significant — of premature births among mothers who got the vaccine compared to those who received a placebo.
The selection follows the FDA’s earlier decision to approve the first RSV vaccine for the elderly in the United States. Several other options are still being evaluated.
Pfizer’s vaccine for pregnant women, called Abrysvo, is being reviewed ahead of another option submitted to the FDA that would be given to babies — a monoclonal antibody shot meant to provide five months of protection.
RSV is a common disease that is most severe in young infants and the elderly. According to the Centers for Disease Control and Prevention, up to 80,000 children younger than 5 years old are hospitalized with the virus each year and up to 300 die. (About 160,000 adults 65 and older are hospitalized each year because of the virus, and about 10,000 die.)
The youngest babies face the greatest risk. Data presented at the meeting showed that infants 6 months or younger were twice as likely to be hospitalized compared to older infants or children. Efforts to test the vaccine in infants began in the 1960s but were abandoned when the vaccine caused more severe cases, said Dr. Bill Gruber, head of clinical vaccine research and development at Pfizer.
The prospect of having more babies immunized in the fall, before winter when RSV levels are typically highest, would be “huge,” Dr. Jonathan Miller, a pediatrician who sees children in clinics and hospitals for Nemours Children’s Health. , Delaware Valley.
“I am very excited about this prospect, as well as the prospect of other RSV vaccines in the pipeline,” said Dr. Miller, who is not the agency’s counsel. “This looks like it’s going to be the first one to come, and it’s been a long time coming.”
The vaccine reviewed Thursday was tested on about 7,300 women after the 24th week of pregnancy. About half received a placebo, and half were given the vaccine as a shot. For the first 90 days after birth, six babies in the vaccination group had serious cases of RSV, compared with 33 in the placebo group, for an efficacy of almost 82 percent.
The study, published in The New England Journal of Medicine, showed that six months after birth, the vaccine was 69 percent effective. In the treatment group, 19 babies were seriously ill compared to 62 in the placebo group.
The main safety concern during the hearing was whether the vaccine was linked to premature birth, a safety signal that prompted GSK to stop testing the same RSV vaccine it tested in pregnant patients, according to Dr. Hal Barron, former company. executive. The FDA approved the vaccine, called Arexvy, for older adults earlier this month. (Like GSK, Pfizer is testing the same vaccine formula in adults and infants.)
“We quickly stopped the trial based on confirmation that the signal was real,” said Dr. Barron’s in a March 2022 presentation to investors, “but we’re still confused as to why this happened.”
The label for the GSK vaccine states that in tests of pregnant women, 6.8 percent of those who received the treatment had premature births, compared to 5 percent in the placebo group.
In the Pfizer study, premature delivery was reported in 5.6 percent of pregnancies in the treatment group, compared with 4.7 percent in the placebo group. Officials at the FDA reported that the difference was not statistically significant.
Pfizer said that if the drug is approved, the company will conduct post-approval studies of the vaccine’s real-world use, monitoring health records for the incidence of premature births and other issues. However, agency advisers expressed skepticism about plans to use data generated from health care billing records to monitor vaccine safety. Some noted that the data could make it difficult to link the parent who got the vaccine to the child.
“I think we need to set a higher bar for review,” said one adviser, Dr. Amanda Cohn, director of the division of birth defects and infant disorders at the CDC, added that more data could help clarify questions about the problem. effects on preterm birth.
Dr. Hana El Sahly, chairman of the advisory committee and professor of virology at Baylor College of Medicine, said that the number of premature births among those given the vaccine in the previous Pfizer study, in the main study reviewed and in the GSK study of the product were similar, especially given that The United States is not in the midst of an RSV outbreak. He said the pattern should be examined more closely.
“This is a missed opportunity and I think it’s unfair that we’re kicking the can down the road to the greater public,” said Dr. El Sahly, who voted “no” to the question of whether the safety data is sufficient.
There is another drug under regulatory consideration, a monoclonal antibody shot developed by Sanofi and AstraZeneca, called nirsevimab. It should be given in hospitals to babies born in winter or autumn, Jonathan Heinrichs, a Sanofi executive, said in an interview.
The drug is under FDA review and was found in one study of nearly 2,500 infants to reduce severe RSV cases by 75 percent.
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