Pfizer vaccine recipients are now being monitored for possible symptoms of Bell's Palsy Syndrome.
It's a condition which paralyzes part of the face, affecting facial muscles.
Eight cases of Bell's Palsy were reported among the 30,000 clinical trial participants.
Seven of them received the vaccine during the trial and developed symptoms between 22 days and 32 days after inoculation.
The other was in the placebo group.
While there is not enough evidence right now to prove a direct link, the FDA says, efforts should be made to look further into the issue for any possible connections.