FDA panel recommends RSV vaccine to protect young babies

A Food and Drug Administration advisory panel on Thursday voted to approve a vaccine from Pfizer to prevent the severe respiratory virus that poses a potentially deadly threat to infants.

The vaccine would be the first to protect babies against respiratory syncytial virus, or RSV, which is why many babies are admitted to children’s hospitals each year, killing hundreds of children under 5 each year.

Fourteen agency advisors unanimously agreed that the vaccine was effective, and the FDA generally follows the recommendations of its advisory panels.

Ten of the 14 agreed that the vaccine was safe, with some concern about increased rates — not all of them statistically significant — of preterm birth in mothers who received the vaccine compared to those who received a placebo.

The vote follows the FDA’s earlier decision to approve the first RSV vaccine for older adults in the United States. Several other options are still being evaluated.

The Pfizer vaccine for pregnant women, called Abrysvo, is under review pending another option submitted to the FDA that would be given to infants: a monoclonal antibody designed to provide five months of protection.

RSV is a common condition that is most serious in young babies and older adults. According to the Centers for Disease Control and Prevention, up to 80,000 children under age 5 are hospitalized with the virus each year, and up to 300 die. (As many as 160,000 adults age 65 and older are hospitalized with the virus each year and about 10,000 die.)

The youngest infants are most at risk. Data presented at the meeting showed that babies 6 months or younger were twice as likely to be hospitalized compared to older babies or children. Attempts to test a vaccine in infants began in the 1960s but were halted when the vaccine caused more serious cases, said Dr. Bill Gruber, the head of clinical vaccine research and development at Pfizer.

The prospect of having a large number of babies immunized in the fall, before winter when RSV rates are typically highest, would be “huge,” said Dr. Jonathan Miller, a pediatrician who sees children in the clinic and hospital for Nemours Children’s Health. , Delaware Valley.

“I’m thrilled at the prospect of this, as well as the prospect of other RSV vaccines in the pipeline,” said Dr. Miller, who is not an advisor to the agency. “This looks like this is the first one coming our way, and it’s taking a long time.”

The vaccine under review on Thursday was tested in about 7,300 women after the 24th week of pregnancy. About half received a placebo and the other half received the vaccine as an injection. During the first 90 days after birth, six babies in the vaccine group had a severe case of RSV, compared to 33 in the placebo group, representing an efficacy of almost 82 percent.

The study, published in The New England Journal of Medicine, showed that the vaccine was 69 percent effective for six months after birth. In the treatment group, 19 babies became seriously ill compared to 62 in the placebo group.

The main safety issue at the hearing was whether the vaccine was linked to preterm birth, a safety signal that led GSK to halt the trial of a similar RSV vaccine that was being tested in pregnant patients. according to Dr. Hal Barron, a former business executive. The FDA approved that vaccine, called Arexvy, for older adults earlier this month. (Like GSK, Pfizer tested the same vaccine formula in older adults and infants.)

“We quickly stopped the trial because it confirmed the signal was real,” said Dr. Barron in a presentation to investors in March 2022, “but we still don’t know exactly why this happened.”

The label for the GSK vaccine says that in tests of pregnant women, 6.8 percent who received the treatment had preterm birth, compared to 5 percent in the placebo group.

In the Pfizer study, preterm birth was reported in 5.6 percent of pregnancies in the treatment group, compared to 4.7 percent in the placebo group. Officials at the FDA reported that the difference was not statistically significant.

Pfizer said if the drug were approved, the company would conduct a post-approval study of the real-world use of the vaccine, checking medical records for the incidence of preterm birth and other potential problems. However, Agency advisers were skeptical of a plan to use data generated from healthcare billing data to monitor vaccine safety. Several noted that such data could make it difficult to link a parent who received the vaccine to the child.

“I feel like we need to raise the bar for assessment,” said one consultant, Dr. Amanda Cohn, the director of the Division of Birth Defects and Infant Disorders at the CDC, added that more data could help answer questions about its effects on preterm birth.

Dr. Hana El Sahly, chair of the advisory committee and professor of virology at Baylor College of Medicine, said the rate of preterm births among those who received the vaccine in a previous Pfizer study, in the main study under review and in the GSK study of a similar product were concerning, especially given that the United States is not in the midst of an RSV outbreak. She said the pattern should have been examined more carefully.

“That was a big missed opportunity and I think it’s unfair that we kicked the can on the road to the wider public,” said Dr. El Sahly, who voted “no” when asked if the security data was adequate.

There is another remedy under legal consideration, a monoclonal antibody developed by Sanofi and AstraZeneca called nirsevimab. It’s meant to be given at the hospital to babies born in the winter or fall, Jonathan Heinrichs, a director of Sanofi said in an interview.

The drug is under review by the FDA and has been found in one study of nearly 2,500 babies to reduce cases of severe RSV by 75 percent.