COVID vaccines may be safe even after an allergic reaction, study finds

COVID-19 vaccine vials. (Robin Lubbock/WBUR)
COVID-19 vaccine vials. (Robin Lubbock/WBUR)

A new study out of Mass General Brigham suggests that even if you had an allergic reaction to the first dose of an mRNA COVID vaccine, it may still be safe to get the second dose.

Immediate allergic reactions to the vaccine are rare, but when they do happen the Centers for Disease and Control and Prevention’s recommendation is that the person should not get the second dose of the vaccine. However, a study published Tuesday in JAMA Network Open suggests that guidance may need updating.

“If you had allergy symptoms after dose one, the majority of people, if they go for dose two, don't have those same symptoms,” said Kim Blumenthal, an author of the study and an allergist at Massachusetts General Hospital.

Blumenthal and her colleagues examined data from almost 53,000 health care employees at Mass General Brigham who received the mRNA vaccine and, within that group, 474 reported a history of high-risk allergies. She said there were two key findings.

First, that people who had a history of high-risk allergic reactions were two times more likely to have an allergic reaction to an mRNA vaccine, with hives and swelling being the most common reactions. However, their second finding was that these people were often able to safely complete the two-dose course required for the Pfizer and Moderna mRNA vaccines without serious reactions to the second dose.

Blumenthal said this is particularly important information because boosters are recommended for some people and because mRNA technology is likely to be used in future vaccines.

“This is all so surprising,” said Blumenthal. “It is contrary to everything we’re taught in allergy because most of the time our drug reactions are not something we would ever try again.”

The study's findings echo that of an earlier study which found that, although about 20% of people who had an allergic reaction to the first mRNA dose reported mild reactions to the second dose, "all patients who received a second dose safely completed their vaccination series and could use mRNA COVID-19 vaccines in the future when indicated."

Last week, Canada’s vaccine advisory committee reversed its recommendation for allergic reactions, saying — after consulting a doctor — a person who had a reaction to the first dose of an mRNA vaccine could receive the second dose.


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Gabrielle Emanuel Senior Health and Science Reporter
Gabrielle Emanuel was a senior health and science reporter for WBUR.



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