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Disclosures: The authors report no relevant financial disclosures.
January 22, 2021
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Anaphylaxis rarely reported among first 4 million doses of Moderna vaccine

Disclosures: The authors report no relevant financial disclosures.
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Anaphylaxis was rarely reported among the first 4 million recipients of the second COVID-19 vaccine authorized for use in the United States, the CDC and FDA reported in MMWR.

According to the report, between Dec. 21 and Jan. 10, more than 1,200 adverse events were reported following vaccination with Moderna’s COVID-19 vaccine. Of these, 108 were determined to be allergic reactions and 10 were confirmed as cases of anaphylaxis — equating to 2.5 cases per million doses administered — according to data compiled from the Vaccine Adverse Event Reporting System.

COVID vaccine
The rate of anaphylaxis among those vaccinated with the Moderna COVID-19 vaccine is 2.5 cases per million doses administered.
Credit: Adobe Stock

The report outlined that nine of the cases of anaphylaxis were reported among people with a documented history of allergies or allergic reactions, including five with a history of anaphylaxis. According to the report, the median time between vaccine receipt to symptom onset was 7.5 minutes but ranged from anywhere between 1 and 45 minutes. Of the eight individuals with follow-up information available, all reportedly recovered or had been discharged home.

“Based on this early monitoring, anaphylaxis after receipt of Moderna COVID-19 vaccine appears to be a rare event; however, comparisons of anaphylaxis risk with that associated with non–COVID-19 vaccines are constrained at this time by the limited data available this early in the COVID-19 vaccination program,” members of the CDC COVID-19 Response Team and the FDA wrote in the report.

Moderna’s vaccine was the second COVID-19 shot authorized for emergency use in the U.S. Earlier this month, the CDC and FDA reported that the first vaccine, developed by Pfizer and BioNTech COVID-19, also was rarely associated with anaphylaxis, with 21 cases of confirmed among the first 1,893,360 recipients of the vaccine.

At the time, Nancy E. Messonnier, MD, director of the CDC’s National Center for Immunization and Respiratory Diseases, said the number “may seem high, but this is still a rare outcome.”

As a precaution, researchers said that vaccination sites should be outfitted to handle these reactions should they arise, and the CDC has issued updated interim clinical considerations to reflect that.

“Locations administering COVID-19 vaccines should adhere to CDC guidance, including screening recipients for contraindications and precautions, having necessary supplies and staff members available to manage anaphylaxis, implementing recommended postvaccination observation periods, and immediately treating suspected anaphylaxis with intramuscular epinephrine injection,” the authors of the new report wrote.