A panel of outside advisers to the U.S. Food and Drug Administration (FDA) voted to endorse a vaccine from Pfizer for respiratory syncytial virus (RSV) on Tuesday.
The majority vote to endorse Pfizer’s product brings it closer to potentially becoming the first approved vaccine for RSV for older adults in the United States. The FDA had granted priority review to Pfizer’s application for the vaccine in December 2022.
Unlike typical past vaccine recommendations, the 12 members of the Vaccines and Related Biological Products Advisory Committee (VRBPAC) were not unanimous in their vote for Pfizer’s product, called Abrysvo (RSVPreF).
For two questions (pdf) on whether Pfizer’s data in a clinical study it conducted were enough to support the safety and efficacy of the vaccine to prevent lower respiratory tract disease caused by RSV in those 60 years or older, the panel voted 7–4 in favor of the drug, with one abstaining member.
While the FDA does not have to follow the advisers’ recommendation, it typically does. The agency will consider the panel’s recommendation and make a decision on Pfizer’s vaccine by May.
Concerns Over Lack of Data in High-Risk Groups
The vote to endorse Pfizer’s RSV vaccine on Tuesday came despite concerns about potential rare reactions, including Guillain-Barré syndrome, as well as concerns over lack of data on how the vaccine performs in populations vulnerable to RSV.
RSV is a common virus that typically causes mild cold-like symptoms for most people. However, in the very young, the elderly, or people with compromised immune systems, RSV can be life-threatening.
The virus can cause infections in the lower respiratory tract and can result in pneumonia. RSV is estimated to cause around 14,000 deaths among older adults in the United States each year.
Pfizer’s vaccine, according to the company’s phase 3 study, was 85.7 percent effective at preventing lower respiratory tract illness in patients with three or more symptoms, and 66.7 percent effective in doing so for patients with two or more symptoms.
But panelists noted there were few people with underlying health problems in the study.
“It’s disappointing we don’t have more data on the high-risk groups and severe outcomes,” said Dr. Daniel Feikin, a respiratory disease consultant who voted in favor of the vaccine. He and other panelists said the FDA should require more data on safety and effectiveness in Pfizer’s planned follow-up study.
Concerns Over Guillain-Barré Syndrome
Much of Tuesday’s meeting among the VRBPAC members revolved around two cases of Guillain-Barré syndrome, a neurological disorder in which the body’s nerves are compromised. Symptoms of the disorder can range from brief weakness in limbs, to paralysis all over the body. But most people recover, even in severe cases.
Guillain-Barré syndrome was diagnosed in two people in their 60s out of 19,942 vaccine recipients in Pfizer’s phase 3 trial of the RSV vaccine, according to an FDA briefing document (pdf) published Feb. 28.
FDA advisers who voted against the Pfizer RSV vaccine’s safety profile cited the two Guillain-Barré syndrome cases.
“I think we need to do everything we can to make sure that vaccines are safe before we send them out to the public,” said Dr. James Hildreth of Meharry Medical College.
The FDA, in its briefing document, noted that the incidence of Guillain-Barré syndrome in the general population is 3 per 100,000 people a year and said that Pfizer should regard the situation as an “important potential risk” to safety.
“To assess the risk of GBS and other immune-mediated demyelinating conditions among RSVpreF recipients post-licensure, FDA has requested that the Applicant propose a postmarketing safety study,” the agency stated.
Pfizer, in its briefing document (pdf), said the Guillain-Barré syndrome cases could have been due to other medical factors. Pfizer said that “at this time,” it has “not identified any safety concerns from the clinical trial safety data.”
“Pfizer will conduct a post-marketing safety study in the older adult population to further assess GBS and immune-mediated demyelinating conditions. To determine the safety of Abrysvo in immunocompromised older adult participants, Pfizer will conduct a postmarketing safety study,” the company said.
Efforts to develop RSV vaccines suffered a major setback in the 1960s when one experimental shot was shown to worsen infections in children.
Public interest in a potential RSV vaccine peaked in the fall of 2022 during a surge of cases affecting babies and older Americans. Pfizer and GlaxoSmithKline are currently only applying for FDA vaccine approval among those who are 60 years old and up.
The FDA panel is set to review and vote on GSK’s vaccine on Wednesday.
The Associated Press contributed to this report.
From The Epoch Times
