Food and Drug Administration advisers this week recommended that the agency approve two RSV vaccines for the elderly, one from Pfizer and the other from GlaxoSmithKline.
The next step is for the FDA to approve each vaccine, which could take several months, although the agency generally follows the recommendations of the advisory committee. After FDA approval, the Centers for Disease Control and Prevention must recommend the injections before they are made available to the public. If all of this happens, the shots would be the first respiratory syncytial virus vaccines to be approved in the United States.
Recommendations from FDA advisers came in separate meetings on consecutive days. On Tuesday, the Independent Advisory Committee on Vaccines and Related Biologicals voted 7 to 4 to recommend Pfizer’s vaccine based on its effectiveness, with one abstention. According to Pfizer, the single-dose vaccine has been shown to reduce the risk of illness from respiratory syncytial virus by up to 86% in people aged 60 and older.
Then on Wednesday, the 12 voting members of the committee unanimously recommended GSK’s vaccine for the same age group based on its effectiveness. Trial data published this month in the New England Journal of Medicine showed the vaccine reduced the risk of symptomatic disease by 83% and severe disease by 94% in people aged 60 and over.
RSV causes lower respiratory tract disease, although for most healthy adults, symptoms are mild. In severe cases, however, RSV can lead to bronchiolitis, which inflames the airways and clogs them with mucus or pneumonia.
The elderly and infants are particularly vulnerable to such outcomes. RSV kills more than 10,000 people age 65 or older and about 300 children under age 5 each year in the United States. Cases rose dramatically in infants this winter, which overwhelmed children’s hospitals – a reminder of the threat of the virus.
Some members of the advisory committee seemed to have more hesitation about Pfizer’s vaccine than GSK’s. Several of the experts expressed concern that insufficient numbers of participants in Pfizer’s trial were infected with RSV to properly assess the effectiveness of the vaccine.
In terms of safety, some advisers have expressed concern about the potential association of the Pfizer vaccine with Guillain-Barré syndrome, a rare neurological disorder that damages nerve cells and causes muscle weakness or paralysis. A man in the Pfizer trial developed Guillain-Barré syndrome, or GBS, after receiving the vaccine, and a woman developed Miller Fisher syndrome, a rare nerve disorder linked to Guillain-Barré.
“It was a 1 in 9,000 GBS risk, which is concerning,” said Dr. Hana El Sahly, chair of the FDA advisory committee.
The FDA asked Pfizer to conduct another study to assess the risk of Guillain-Barré syndrome after its vaccine was approved.
In the GSK trial, the FDA identified one case of Guillain-Barré potentially linked to the vaccine, as well as a higher number of incidences of atrial fibrillation (irregular heartbeat) in vaccinees compared to the control group.
“There are challenges, possible safety signals, but I think the data warrants a ‘yes’ vote,” Dr. James Hildreth, committee member and president of Meharry Medical College, said of the GSK firing. .
In terms of other side effects, the most commonly reported in GSK’s trial were pain at the injection site, fatigue and muscle aches. At Pfizer, the most common were fatigue, headache, pain at the injection site and muscle aches, according to an FDA backgrounder.
GSK’s trial participants reported side effects more frequently than Pfizer’s.
The race for the RSV vaccine
Several companies have been rushing to get FDA approval for RSV vaccines.
Eleven RSV vaccines are being actively studied in US trials, according to data from PATH, a global health nonprofit organization.
Moderna said an RSV vaccine it had developed for the elderly could be submitted to the FDA by July. Bavarian Nordic expects to have late-stage trial data for its RSV vaccine, which targets the same demographic, by mid-year.
The FDA is also reviewing data from trials of a monoclonal antibody injection designed to protect babies from RSV, which works similarly to a vaccine. The shot, from Sanofi and AstraZeneca, has already been approved in Europe.
Meanwhile, Pfizer has been testing its RSV vaccine in pregnant women to see if protection can be passed to babies in utero. The company said its data suggests the vaccine reduced the risk of severe disease in infants by 82% during their first 90 days of life and by 69% for six months.
But the FDA committee’s vote was limited to the use of the Pfizer vaccine for the elderly. The agency is still reviewing data for pregnant women, with a decision expected in August.