CDC confirms 29 anaphylaxis cases after COVID-19 vaccination, calls them ‘exceedingly rare’

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Federal health officials have confirmed 29 cases of anaphylaxis after COVID-19 vaccination but are emphasizing the vaccine is safe as millions of doses have been administered.

Anaphylaxis is “still exceedingly rare,” said Nancy Messonnier, M.D., director of the Centers for Disease Control and Prevention’s (CDC’s) National Center for Immunization and Respiratory Diseases. “Of course, we all would hope any vaccine would have zero adverse events but … it’s a very safe vaccine.”

Twenty-one of the cases were detailed today in a Morbidity and Mortality Report looking at doses of the Pfizer-BioNTech vaccine distributed Dec. 14-23, 2020.

Those cases occurred among nearly 1.9 million doses administered, a rate of 11.1 per 1 million doses. Dr. Messonnier acknowledged the rate is significantly higher than the 1.3 cases per million for flu vaccines but said officials have not detected worrisome safety signalsand are continuing to track and investigate cases.

“Right now, the known and potential benefits of the current COVID-19 vaccines outweigh the known and potential risks of getting COVID-19,” she said.

The median age of the first 21 anaphylaxis cases was 40 years and 90% were female. The average time between vaccination and symptom onset was 13 minutes. Most reactions occurred within 15 minutes. Officials said the doses came from multiple lots of the vaccine, and there was no clustering in any one area of the country.

Seventeen of those who experienced anaphylaxis had a history of allergic reactions to drugs, medical products, food or insect stings. Seven had a history of anaphylaxis.

Four of the patients were hospitalized including three in intensive care. No deaths were reported. Among the 20 with available data, all had been discharged home or recovered, according to the report.

The eight additional cases announced in a press briefing Wednesday that were not part of the study involved both the Pfizer-BioNTech and Moderna vaccines, but no additional details were available. No cases of anaphylaxis were reported in the companies’ clinical trials.

Officials said the cases in recent weeks highlight the need for people administering vaccines to screen patients and to have the necessary supplies and training to recognize and treat anaphylaxis (see resources).

The CDC says people should not receive a COVID-19 vaccine if they have a history of severe allergic reaction or an immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components, including polyethylene glycol. They also should not be vaccinated if they have a history of immediate allergic reaction of any severity to polysorbate.

People with a history of any immediate allergic reaction to any other vaccine or injectable therapy can receive the vaccine but should be counseled about the risks. Those with this history or a history of anaphylaxis due to any cause should be observed for 30 minutes after vaccination. All others should be observed for 15 minutes.

During the week and a half period in the study, 83 cases of nonanaphylaxis allergic reactions also were reported, 87% of which were classified as nonserious, according to the report. Both vaccine manufacturers have said reactions after vaccination are common but typically mild to moderate, including pain at the injection site, fatigue, headache, myalgia, arthralgia, nausea/vomiting, chills and fever.