Thread by @nytimes

Concerns have mounted among those with allergies following news that two British health care workers suffered severe reactions after receiving Pfizer’s coronavirus vaccine.

Here's what you need to know: nyti.ms/37ausBq

“How common will these reactions be?”

They’re rare. In Pfizer’s late-stage clinical trial, just one of the 18,801 vaccine recipients had a severe reaction. In Britain, both patients had a history of anaphylaxis, and both recovered following treatment. nyti.ms/37YW7nT

“But didn’t Pfizer catch this in its clinical trials?”

People with a history of anaphylaxis to any vaccine were excluded from Pfizer's studies.

In the U.S., the FDA will require Pfizer to increase its monitoring for anaphylaxis and submit data on it. nyti.ms/37YW7nT

“If I have allergies, should I be concerned?”

Dr. Anthony Fauci, the nation’s leading expert on infectious diseases, said on Wednesday that those with severe allergies should be prepared just in case. nyti.ms/37YW7nT

“Should people with allergies avoid Pfizer’s vaccine?”

No. Fewer than one in a million recipients of other vaccines a year in the U.S. have an anaphylactic reaction.

Reactions are treatable, and much easier to control than a severe case of Covid-19. nyti.ms/37YW7nT

For more information about allergic reactions to Pfizer’s coronavirus vaccine: nyti.ms/37YW7nT