Everyone who experienced an allergic reaction to their first dose of an mRNA-based COVID-19 vaccine tolerated the second dose without complications in a multihospital study led by researchers at Massachusetts General Hospital in Boston.
The study, published July 26 in JAMA Internal Medicine, found that among 189 patients, 32 experienced anaphylaxis after their first dose of an mRNA vaccine. A total of 159 patients received a second dose, and all of them, including 19 who experienced anaphylaxis after their first dose, tolerated the second dose. Thirty-two patients reported immediate and potentially allergic reactions to the second dose, but they were mild or resolved with antihistamine alone.
All of the patients who had a reaction after the first dose were advised by allergy specialists.
The findings suggest that it's safe for most people to receive a second dose of the COVID-19 vaccine, even if they experienced an allergic reaction to the first, the study's authors said.
Anaphylaxis after an mRNA vaccine has occurred in up to 2.5 per 10,000 people vaccinated, the authors said. First-dose allergic reactions typically include symptoms such as itching, hives and flushing.
The study included researchers from Vanderbilt University Medical Center in Nashville, University of Texas Southwestern Medical Center in Dallas and Yale School of Medicine in New Haven, Conn. It was funded by the National Institutes of Health and Massachusetts General Hospital.