CDC says chance of anaphylaxis from COVID-19 vaccine is 11 in 1 million: 'Exceedingly rare'

Abby Haglage
·4 min read

An estimated 5.3 million Americans have received the first dosage of COVID-19 vaccines as of Wednesday, according to a tracker from the Centers for Disease Control and Prevention. And although the vaccines have been deemed safe, reports show that many nursing home residents and health care workers — both of whom are top priority for vaccination — remain reluctant to get vaccinated.

A new report from the CDC details 21 cases of anaphylaxis following the COVID-19 vaccine. But officials say the reaction remains "exceedingly rare." (Photo: Getty Images)
A new report from the CDC details 21 cases of anaphylaxis following the COVID-19 vaccine. But officials say the reaction remains "exceedingly rare." (Photo: Getty Images)

In a call with the media Wednesday, Dr. Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases, attempted to allay concerns about one potential side effect: severe allergic reactions leading to anaphylaxis. Reports of anaphylaxis following a COVID-19 vaccine first emerged in the U.K. in early December, followed by several reports of severe allergic reactions in the U.S., including among two Alaska health care workers.

But the reaction, the CDC says, is both “exceptionally rare” and treatable — posing much less risk for Americans than COVID-19.

Messonnier told reporters that the CDC recorded 21 cases of anaphylaxis total among the first 1.89 million Americans vaccinated (from December 14–23) which translates to a rate of 11 cases out of 1 million. In a paper published Wednesday, the CDC expanded on the information, revealing that 17 of the individuals had a “documented history of allergies or allergic reactions,” and seven of them had experienced anaphylaxis in the past. Follow-up information was available for 20 of the individuals, all of whom “had recovered or been discharged home” by the time of the report.

Anaphylaxis, according to the Mayo Clinic, is a “potentially life-threatening allergic reaction” that causes symptoms such as a “rapid, weak pulse; a skin rash; constriction of the airwaves; nausea and vomiting.” The condition is an overreaction of the immune system that often occurs minutes after exposure to an allergen. It can be successfully treated with epinephrine, also known as an EpiPen. Medication, food and insect stings are the three top causes of the condition, which 1.6 percent of Americans will experience in their lifetime.

“It's still exceedingly rare,” Messonnier said on the call. “Of course, we all would hope that any vaccine would have zero adverse events but even at 11 cases per million doses administered, it’s a very safe vaccine. We’re in the setting of 2,000 COVID deaths per day, and if you make that comparison, I would say it’s still a good value proposition for someone to get vaccinated. Their risk [of severe outcomes] from COVID-19 ... is still more than their risk of a severe outcome from the vaccine.”

In a statement to Yahoo Life, Pfizer said it “closely monitors” any reports of serious allergic reactions following vaccinations and plans to “update labeling” if necessary. “The prescribing information has a clear warning/precaution that appropriate medical treatment and supervision should always be readily available in case of a rare anaphylactic event following the administration of the vaccine,” the spokesperson said. Moderna has not responded to Yahoo Life’s request for comment.

As of now, it’s still unclear exactly what may be causing the reactions, but the Food and Drug Administration’s director of the Center for Biologics Evaluation and Research suggested in mid-December that they may be related to a chemical called polyethylene glycol (PEG), which is present in both the Moderna and Pfizer vaccines. The FDA has recommended that those who have had severe allergies to vaccines in the past avoid both the Pfizer and Moderna vaccines.

Still, Messonnier says that the rare reactions should not deter Americans who have a history of allergies from getting the vaccine. “Our recommendation is that folks should be consulting with their health care provider,” says Messonnier. “There is a big difference from somebody who had a mild allergic reaction in their childhood versus somebody that had a severe allergic reaction last week. And it’s going to be really important to have a clinician able to help a patient exercise judgment as opposed to having sort of completely hard and fast rules.”

For the latest coronavirus news and updates, follow along at According to experts, people over 60 and those who are immunocompromised continue to be the most at risk. If you have questions, please reference the CDC’s and WHO’s resource guides.

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