The US Food and Drug Administration has asked the drug company Pfizer to conduct a safety study after two people who received its respiratory syncytial virus vaccine in a clinical study were later diagnosed with Guillain-Barre Syndrome, a rare brain disorder.
In documents released on Friday, the agency asked the drug company to complete the study if the shot is approved to ensure no great risk to anyone who receives it.
As for the two people who were diagnosed with the brain disorder, both were adults in their 60s, the paperwork shared. They were among 20,000 people to have received Pfizer’s shot in its Phase 3 clinical trial.
Guillain-Barre Syndrome is a neurological disorder that is considered to be rare and causes the immune system to attack its own nerves, resulting in muscle weakness and, in some cases, paralysis, according to the Mayo Clinic.
However, the disease is not always permanent, as most people recover fully, though some cases can be fatal or have lasting effects. The FDA estimates that the incidence of Guillain-Barre is 1.5 to 3 cases for 100,000 adults over the age of 60 in the US annually.
As for those who developed the disorder, within three months of the diagnosis, one of the individuals had recovered, and the other was said to be improving after six months. The documents shared that among those who didn’t receive the shot, no cases of Guillain-Barre Syndrome were reported.
Because of this, the FDA is seriously considering the brain condition a risk of the vaccine, it noted in its documents.
“Given the temporal association and biological plausibility, FDA agrees with the assessments of the investigators that these events were possibly related to study vaccine. … Therefore, [Guillain-Barre] is being considered an important potential risk,” the FDA said in its documents.
The release of the documents comes before the agency’s Vaccines and Related Biological Products Advisory Committee meeting, which consists of independent vaccine advisers. The meetings are slotted for Tuesday and Wednesday of this week.
Among the topics on the table for the committee are two RSV vaccines for adults 60 and older. The vaccines are from Pfizer and GSK, and the committee is expected to discuss and make recommendations for both.
Being that Guillain-Barre Syndrome is being discussed internally at the FDA, it is expected to be a topic of discussion for the committee surrounding the Pfizer vaccine.
“Given the higher than background rate of GBS observed in the Phase 3 study, FDA will recommend a postmarketing study and enhanced surveillance for further evaluation of GBS and other immune-mediated demyelinating conditions with postmarketing use,” the FDA says.
Pfizer is also prepared to provide evidence that the cases can be explained for reasons other than the vaccine and that its shot is a “well-tolerated and safe vaccine, with a benefit-to-risk ratio that is favorable,” documents about next week’s meetings show.
Nonetheless, Pfizer says a safety study on Guillain-Barre syndrome will be conducted if its RSV shot is approved.
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