In its review of the new COVID-19 vaccine developed by Pfizer Inc. and BioNTech SE, the Food and Drug Administration disclosed that four recipients of the vaccine in clinical trials developed Bell's palsy, a sudden, temporary weakness in facial muscles. The FDA said the rate (.0009% of trial participants) is comparable to what's seen in the general U.S. population (.001%, or about 40,000 cases a year).
The U.K. has already approved the vaccine for use. On December 9, two days after it began administering the vaccine, authorities said an allergic reaction causing anaphylaxis had occurred in two recipients. Anaphylaxis, while severe, is very rare, and a known risk with any vaccine. Anyone with a history of anaphylaxis due to a vaccine, medicine or food is being advised not to take the Pfizer/BioNTech vaccine.