To look more closely at the risk of allergic reactions to the vaccines, researchers from the Mass General Brigham health care system analyzed data from almost 53,000 of its employees to see if an association existed between a history of allergic reactions to medications, vaccines, or other allergens and self-reported allergic reactions following administration of an mRNA COVID vaccine. About 470 employees reported a history of high-risk allergic reactions. However, almost 98 percent of all study participants successfully received both doses of an mRNA vaccine.
Knowing this information can help guide conversations between providers and their patients who might be reluctant to get the mRNA COVID vaccine because of a history of allergic reactions or allergy concerns, Lily Li, lead author on the study, told TheDoctor. “The study contributes to the body of evidence regarding the safety of mRNA COVID vaccines, which will be important going forward now that third doses are recommended.”
The most common allergic reactions were hives and angioedema, a temporary accumulation of fluid and swelling in the skin and mucous membranes.
Employees of Mass General Hospital received at least one dose of a COVID mRNA vaccine between December 14, 2020 and February 1, 2021 and completed a post-vaccine symptom survey within three days of vaccination. Demographic data, medical records and vaccine data were also analyzed, and a follow-up period ran until March 1, 2021.
More studies are needed to better understand the possible factors, including gender, that may affect the risk of allergic reactions to mRNA vaccines, the researchers said. Most allergic reactions seem to happen after the first dose, which is unusual for IgE-mediated allergic reactions, such as those two vaccines, according to Li, an instructor of medicine at Harvard Medical School. Most people have a mild reaction or no reaction when they get the second dose. “So a lot of work looking at the possible mechanisms underlying reactions to mRNA vaccines needs to be done.”
The rate of allergic reactions reported after an mRNA vaccine has only been about two percent.
The study is published in JAMA Network Open.