The Food and Drug Administration sees a possible risk of Guillain-Barre syndrome with Pfizer’s RSV vaccine for older adults and has asked the company to conduct a safety study if the shot is approved this spring, according to agency briefing documents published Friday.
Two people in their 60s who received Pfizer’s shot were diagnosed with Guillain-Barre syndrome, out of about 20,000 vaccine recipients in the phase three trial, according to the FDA document. There were no cases in the trial’s placebo group, the people who didn’t receive the shot.
Guillain-Barre syndrome, or inflammatory neuropathy, is a rare disorder in which the body’s immune system mistakenly attacks the nerves. Symptoms range from brief weakness to paralysis, according to the National Institutes of Health. Most people recover, even from severe cases.
Pfizer, in its briefing document, said the cases have other possible explanations. But it said it will conduct a safety study to further assess Guillain-Barre syndrome after a potential approval. The company said it did not identify any safety concerns during the trial and the vaccine was well tolerated.
There was also a possible case of Guillain-Barre syndrome in GSK’s RSV vaccine trials, but the company said there was insufficient evidence to confirm a diagnosis. GSK has listed Guillain-Barre as an important potential risk in its safety surveillance plan, according to the FDA. The agency said it will review the plan and make recommendations as needed.
The FDA published the briefing documents ahead of its advisory committee meetings next week. The advisors will vote Tuesday on whether Pfizer’s efficacy and safety data supports an FDA approval. They will also vote Wednesday on GSK’s RSV vaccine for older adults.
No approved RSV vaccine exists. The virus causes anywhere from 6,000 to 10,000 deaths a year among seniors, though mortality varies from season to season. According to an FDA review of the companies data, Pfizer’s vaccine was 85% effective at preventing lower respiratory tract illness and GSK’s shot was 83% effective.