FDA advisers barely vote in favor of Pfizer’s RSV vaccine for older adults, despite potential safety concerns


Vaccine advisers to the US Food and Drug Administration on Tuesday narrowly voted in favor of Pfizer’s RSV vaccine for adults over 60, clearing the way for approval of the nation’s first RSV vaccine, despite some safety concerns.

Committee members voted 7–4, with one abstention, that there are sufficient data to support the safety and effectiveness of Pfizer’s vaccine for the prevention of lower respiratory tract disease caused by respiratory syncytial virus among older adults.

The FDA, which usually follows the independent committee’s recommendations, is scheduled to approve the vaccines by May, ahead of RSV’s typical winter surge. The US Centers for Disease Control and Prevention must then recommend the shot before it becomes available to the public.

Pending those steps, Pfizer’s vaccine — along with GSK’s candidate shot, which will be voted on by the FDA’s advisory committee on Wednesday — will be the first approved RSV vaccines for adults age 60 or older.

RSV is a highly contagious virus that causes flu-like illnesses in people of all ages that increase in severity with age. It is responsible for an estimated 177,000 hospitalizations and 14,000 deaths per year among adults 65 or older, according to the CDC.

The Pfizer vaccine was 66.7% effective in preventing moderate lower respiratory disease with two or more symptoms and 85.7% effective in preventing disease with three or more symptoms, according to an FDA document.

Although a majority of the committee voted in favor of the vaccine, some members expressed concern about the vaccine’s “significant potential risk: Guillain-Barre syndrome. Two adults among the 20,000 vaccine recipients in Pfizer’s Phase 3 clinical trial developed symptoms consistent with the rare neurological disorder within nine days of receiving the shot.

“It seems to me that one case is a red flag. Two cases are very concerning, and it worries me that Pfizer doesn’t think there are any safety concerns,” said Dr. Marie Griffin, professor of health policy at Vanderbilt University Medical Center, who agreed that the data showed the vaccine was effective but not safe.

The FDA has recommended that Pfizer conduct a safety study to further evaluate Guillain-Barre and other immune-mediated demyelinating conditions following potential vaccine approval, and the company has agreed.

Respiratory disease consultant Dr Daniel Feikin, who voted the vaccine was both safe and effective, said post-marketing safety monitoring will be “critical”.

Some of the vaccine advisors wanted to see more data on effectiveness against hospitalization or death, especially among high-risk people such as older adults or those with other health conditions.

“I think the data supports the effectiveness of this vaccine. It’s just the population that was underrepresented by people who could benefit the most from the vaccine,” Griffin said.

The available safety and efficacy data from Pfizer’s clinical trial are from the first of two RSV seasons. Some of the experts said the poll is too early and they would like to see more data.

“I am desperately anxious to get a vaccine that works for RSV. This has been a terrible disease my entire career. I would like to see it. No doubt about it, said Dr. Jay Portnoy, a professor of pediatrics at the University of Missouri-Kansas City, who agreed that the data showed the vaccine was safe but not effective.

Portnoy says waiting for a second season of data will provide more robust numbers and complete analysis.

“It is not an emergency use permit. We can take the time to complete the studies and get the information we need before we license this product going forward. So I’m still a bit skeptical, given the data we have.”

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