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Acute allergic reactions occurred in 2.10% but anaphylaxis in only 0.025% of employees at two Boston hospitals who received their first dose of the Pfizer-BioNTech or Moderna COVID-19 vaccine, according to a research letter published yesterday in JAMA.
Scientists at Massachusetts General Hospital and Brigham and Women’s Hospital administered an email, text, phone and smartphone app survey to 64,900 employees who received a dose of one of two coronavirus mRNA vaccines from Dec. 16 2020 to February 12, 2021.
MRNA vaccines “teach” human cells to make a harmless part of the SARS-CoV-2 spike protein to trigger an immune response to the virus. The authors noted that people with a history of life-threatening reactions, or anaphylaxis, to allergens such as those in a vaccine are often reluctant to receive vaccines, which can complicate efforts to end the pandemic.
A total of 25,929 employees (40%) received the Pfizer vaccine, while 38,971 (60%) received the Moderna vaccine. Eighty-one percent returned at least one symptom survey, which was sent out every day for 3 days after vaccination.
Of all employees vaccinated, 1365 (2.10%) reported acute allergic reactions, defined in the survey as itching, rash, hives, swelling and / or respiratory symptoms. More Moderna vaccinees (2.20%) reported symptoms than Pfizer vaccinees (1.95%).
Previous anaphylactic episodes
A review of medical records revealed anaphylaxis in 16 workers (0.025%) (9 [0.023%] with Moderna vaccine and 7 [0.027%] with the Pfizer vaccine). The average age of vaccinated people diagnosed with anaphylaxis was 41 years, 94% were female, 63% had a history of allergy and 31% had previously suffered from anaphylaxis.
The mean time between vaccination and the onset of anaphylaxis was 17 minutes. One patient required intensive care, 56% received intramuscular epinephrine (to facilitate breathing) and all recovered without experiencing shock or requiring endotracheal intubation. Three workers with a history of anaphylaxis did not seek medical attention. The mechanism of the occurrences of anaphylaxis in the study is unknown.
The Centers for Disease Control and Prevention previously reported an incidence of anaphylaxis of 2.5 to 11.1 per million doses, most in people with a history of allergy, the authors noted.
“The incidence rate of anaphylaxis confirmed in this study is greater than that reported by the Centers for Disease Control and Prevention based on passive spontaneous reporting methods,” they wrote. “However, the overall risk of anaphylaxis from a COVID-19 mRNA vaccine remains extremely low and broadly comparable to other common healthcare exposures.”
While most people vaccinated with anaphylaxis had a history of allergy, the researchers noted that, given that about 5% of American adults suffer from severe food allergies and 1% suffer from severe drug allergies. , the group of employees studied must have included nearly 4,000 workers with a history of anaphylaxis who were vaccinated without associated adverse events.
“In this potential cohort of healthcare workers, 98% showed no symptoms of an allergic reaction after receiving a COVID-19 mRNA vaccine,” the authors wrote.
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