FDA Panel Endorses GSK Vaccine for RSV in Older Adults, a Day After Recommending Pfizer’s Vaccine

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3/2/2023

Updated:

3/24/2023

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A committee of outside advisers to the U.S. Food and Drug Administration (FDA) recommended a vaccine from GlaxoSmithKline (GSK) against the respiratory syncytial virus (RSV) for adults over age 60.

The vote from the Vaccines and Related Biological Products Advisory Committee (VRBPAC) for GSK’s Arexvy (RSVPreF3-AS01) vaccine comes a day after the 12 members voted to endorse Pfizer’s vaccine candidate, Abrysvo (RSVPreF), for the same age group.

For both vaccines, the members flagged potential safety concerns especially with regard to Guillain-Barré syndrome, a neurological disorder in which the body’s nerves are compromised, symptoms of which can range from brief weakness in limbs, to paralysis all over the body. But most people recover, even in severe cases.

There are currently no RSV vaccines approved in the world. Pfizer and GSK are currently only applying for FDA approval among those who are 60 years old and up.

The 12 advisers voted unanimously on Wednesday that research data support the effectiveness of GSK’s vaccine for RSV in adults 60 and older. They also voted 10–2 that the data support the safety of the vaccine in the age group.

The Pfizer vaccine for RSV had received two separate votes, both 7–4, that research data support the effectiveness and safety of its RSV vaccines in adults 60 and older.

While the FDA does not have to follow the advisers’ recommendations, it typically does.

The FDA will consider the committee’s recommendation and make a decision on GSK’s vaccine by May 3, and on Pfizer’s vaccine by the same month.

Evan Wang, Guggenheim Securities analyst, ahead of the panel vote, said that if approved, peak sales for GSK’s vaccine against RSV are estimated to be about $2.8 billion globally.

RSV Potentially Life-Threatening For Some

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.

RSV 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.

The VRBPAC panelists seemed significantly more confident about the demographic profile used during the GSK study in comparison to Pfizer’s RSV vaccine.

“The population is more representative of those who are going to get the disease ... giving me a lot of comfort in the vaccine” said Jay Portnoy, one of the 12 members of VRBPAC, commenting on the study conducted on the GSK shot.

Data from GSK’s phase 3 trial in October on its RSV vaccine, which were recently published in the New England Journal of Medicine, showed the shot was 82.6 percent effective in preventing lower respiratory tract disease in people 60 and over.

Meanwhile, 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.

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.

Guillain-Barré Syndrome Concerns

The FDA previously expressed concerns over a case of Guillain-Barré syndrome in studies on GSK’s vaccine.

Specifically, one person—a 78-year-old woman from Japan—experienced symptoms consistent with Guillain-Barré syndrome nine days after taking the GSK vaccine, and started immunoglobulin treatment for the disorder, according to an FDA briefing document (pdf).

She was the only case of Guillain-Barré syndrome out of 15,862 people who took the GSK shot. Her symptoms were considered resolved after six months, according to a GSK briefing document (pdf).

The FDA considered the case to be related to the GSK vaccine. GSK, however, has said the reported information is “insufficient to confirm the diagnosis,” noting that “neither a neurological consultation nor electrophysiologic testing were reported,” and that “the reported clinical signs and serological parameters may be present in other neurological disorders.”

According to the FDA, GSK listed Guillain-Barré syndrome as one of the potential risks in its pharmacovigilance plan. The FDA said it is working to review the plan and will make further safety recommendations “as needed.”

Meanwhile, 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).

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. But Pfizer, in its briefing document (pdf), said the reported 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.

Reuters and The Associated Press contributed to this report.

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