- A panel of Food and Drug Administration advisers on Thursday backed maternal use of Pfizer’s RSV vaccine for protecting young infants, but recommended its early use be closely monitored to confirm study safety data.
- The panel of outside advisers voted 14-0 that Pfizer’s vaccine, called Abrysvo, was effective in protecting infants from infections caused by respiratory syncytial virus, or RSV, when given to their mothers during pregnancy.
- Despite some concerns around the shot's potential risk, they agreed in a 10-4 vote that Pfizer's data showed it to be generally safe. The FDA, which usually follows the advice of its advisers, is expected to decide whether to approve maternal use of the shot by August. Separately, its use in older adults is due a decision this month.
The vaccine, if approved, would be the first available for protecting infants from a pathogen that each year kills hundreds of young children. It is one of a recent wave of drugmaker successes against the disease after decades of effort. The U.S. approved the first vaccine for RSV for use in older adults earlier this month and could soon approve a long-acting antibody for RSV in babies that Europe cleared in November.
The panel’s vote on Thursday concerned use of Abrysvo between 24 and 36 weeks of pregnancy, an approach that is meant to pass on immunity to newborns and protect them through 6 months of age. Pfizer’s study results published last month showed the vaccine reduced the risk of severe RSV infection in infants by 82% at 90 days after birth and by 69% at 180 days.
“If the vaccine actually lives up to the data that we've seen today, I can guarantee that many infants and their parents will breathe easier in the coming years,” said panelist Jay Portnoy, a professor of pediatrics at Children’s Mercy Hospital in Kansas City.
Some panel members expressed concern that Pfizer did not have enough data to prove the vaccine’s safety, pointing to data from lower-income countries that showed a higher rate of increased preterm births. Its studies were not designed to determine whether that was a real safety signal, however.
“Hav[ing] 20% increased risk of premature delivery is not trivial,” said the committee’s chair Hana El Sahly, a professor of molecular virology and microbiology, who voted no on the shot’s safety. Pfizer’s late-phase study “should have been designed to answer whether the signal was real or not,” she said. “I feel it’s unfair that we kicked the can down the road to the larger public” with post-marketing surveillance studies.
Several panelists also expressed concern about rival drugmaker GSK halting testing of a maternal RSV candidate last year. That shot has a similar dosage as Pfizer’s shot and “those decisions are never made lightly,” said Paul Offit, a professor of pediatrics at the Children’s Hospital of Philadelphia. “I do think a lot is at stake when you're asking one to protect another.”
There was also concern raised about possible interference with other vaccines when given at the same time. Portnoy said he does not consider that an adverse effect because it can be managed by timing vaccination, and the other risk raised — earlier births — is only harmful to a small number of infants.
“And over 90% of these children [born early] are going to get RSV, and I’ve seen the harm that that does,” Portnoy said. “So if I compare the very small risk of earlier birth with the almost certain risk of getting RSV and a very high risk of ending up in the hospital” the risk is much greater without the vaccine than without.
Earlier this year, the same panel voted 7-4 to recommend the FDA approve Abrysvo for use in adults 60 years and older, but similarly expressed concerns about whether Pfizer’s study results adequately showed the shot was safe in older participants with weak immune systems.