Vaccine advisers to the US Food and Drug Administration narrowly voted Tuesday in favor of Pfizer’s RSV vaccine for adults over the age of 60, paving the way for approval of the first nation’s RSV vaccine, despite some safety concerns.
The committee members voted 7-4, with one abstention, that there is adequate 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 typically follows the independent committee’s recommendations, is scheduled to decide on approval of 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 advisory committee on Wednesday – would be the first approved RSV vaccines for adults 60 or older.
RSV is a highly contagious virus that causes flu-like illness in people of all ages that increases in severity with age. It’s 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 at preventing moderated lower respiratory tract illness with two or more symptoms and 85.7% effective at preventing illness with three or more symptoms, according to an FDA briefing document.
Although a majority of the committee voted in favor of the vaccine, some members expressed concerns about the vaccine’s “important potential risk: of 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 is very concerning, and it’s concerning to me that Pfizer doesn’t think that there are any safety concerns,” said Dr. Marie Griffin, professor of health policy at Vanderbilt University Medical Center, who voted that the data demonstrated the vaccine was effective but not safe.
The FDA has recommended that Pfizer conduct a safety study for further evaluation of Guillain-Barre and other immune-mediated demyelinating conditions after potential vaccine approval, and the company has agreed.
Dr. Daniel Feikin, respiratory disease consultant, who voted that the vaccine was both safe and effective, said that post-marketing safety surveillance will be “critical.”
Some of the vaccine advisers 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 does support the effectiveness of this vaccine. It’s just the population was underrepresented by people who could most benefit from the vaccine,” Griffin said.
The available safety and efficacy data from Pfizer’s clinical trial is from the first of two RSV seasons. Some of the experts said that the vote is premature and that they would like to see more data.
“I’m desperately eager to have a vaccine that works for RSV. This has been a terrible disease my whole career. I would love to see it. No doubt about it,” said Dr. Jay Portnoy, professor of pediatrics at the University of Missouri-Kansas City, who voted that the data demonstrated that the vaccine was safe but not effective.
Portnoy says that waiting for a second season of data would provide more robust numbers and complete analysis.
“It’s not an emergency use authorization. We can take the time to finish the studies and get the information we need before licensing this product going forward. So I remain a little bit skeptical, given the data that we have.”