The FDA said in a news conference on Friday that there have been “roughly" five adverse reactions to Pfizer’s coronavirus vaccine, which began distribution earlier this week.
According to FDA and Pfizer officials, 2.9 million doses of the vaccine was distributed this week. Those doses mostly went to health care workers and those living and working in assisted living facilities. It’s unclear exactly how many of those 2.9 million doses have been administered, as of Friday.
Dr. Peter Marks, director of the Center for Biologics Evaluation and Research, told reporters on Friday that one of the five adverse events caused a serious reaction. Marks did not go into detail on the locations or conditions of all the cases. The FDA has not responded for a request for additional information.
Marks said that a case in Alaska was the most serious of the reactions being investigated.
“We will continue to watch these closely. It is difficult to talk about them without any kind of good certainty until we have more information on them,” Marks said.
FDA officials said that it’s possible the reactions were from the vaccine’s active ingredient polyethylene glycol. According to government information, the ingredient can cause known side effects such as bloating, diarrhea, nausea, cramps, gas and hives.
FDA administrator Dr. Stephen Hahn said that the vaccine’s monitoring program is working well.
“One of the things the FDA does well and uniquely is really getting to the bottom to events like allergic reactions,” Hahn said.
On Friday, a second vaccine received FDA authorization. The vaccine from Moderna received an emergency use authorization, which means the vaccine can now be administered outside of a clinical or hospital setting.