CDC Reports Few Cases of Severe Allergic Reactions to Pfizer COVID-19 Vaccine

Based on reports of close to 2 million vaccinations administered to prevent COVID-19 in the U.S., fewer than two dozen people experienced anaphylaxis, a severe allergic reaction that is a rare risk factor with the vaccine. The Centers for Disease Control and Prevention (CDC) reported the news in the January 6 edition of its weekly journal Morbidity and Mortality Weekly Report.

The study was conducted between December 14 and December 21, 2020, among participants who received the Pfizer-BioNTech vaccine. This was before the Moderna vaccine, the second vaccine authorized for emergency use by the Food and Drug Administration (FDA), was in wide distribution.  

Nearly three-quarters of the 21 anaphylaxis reactions–71%–occurred within 15 minutes of a person receiving a vaccination. That’s important because the FDA currently recommends that people wait at the facility where they received a vaccine for 15 minutes so they can be treated by medical staff if they do have a reaction. 

People who have had any anaphylactic reaction in the past are asked to wait for half an hour, Thomas Clark, MD, MPH, deputy director of the division of viral diseases at the CDC, tells Verywell. Anaphylaxis can be reversed with a drug called epinephrine that health facilities distributing the COVID-19 vaccines must have on hand. 

According to the study, 17 of the 21 people who experienced anaphylaxis had documented histories of allergies or allergic reactions, including seven who had a history of anaphylaxis. 

In a briefing with reporters this week, Nancy Messonnier, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, said that the 21 cases of anaphylaxis translate to a rate of 11.1 cases per million doses. Comparatively, cases of anaphylaxis associated with the flu vaccine appear at rate of 1.3 per million doses, according to the CDC. 

“The anaphylaxis rates for COVID-19 vaccines may seem high compared to flu vaccines,” Messonnier says, “But I want to reassure you this is still a rare outcome."

Messonnier says the CDC has been adapting recommendations as it learns more. For example, the organization recently recommended that anyone who has an immediate or allergic reaction to the first COVID-19 vaccine dose not receive the second dose. And anyone with a history of an immediate allergic reaction to injectable vaccines and people with a history of anaphylaxis from any cause should be observed for 30 minutes after vaccination. 

“Right now, the known and potential benefits of the current COVID-19 vaccines outweigh the known and potential risks [of] getting COVID-19," Messonier says. "The CDC and FDA are rigorously reviewing all serious adverse event reports."

Clark says the CDC plans to do a similar study with the Moderna vaccine.

Other studies confirm what the CDC study shows about the low risk of severe allergic reactions to COVID-19 vaccines. A December 2020 study in the Journal of Allergy and Clinical Immunology looked at allergic reactions in the U.K., where vaccines were administered ahead of the U.S. Results showed that: 

• Allergic reactions to COVID-19 vaccines are rare. 
• Pfizer-BioNTech and Moderna COVID-19 vaccine allergic reactions have a similarly low rate of occurrence. 
• Clinics can manage any allergic reactions that occur. 
• Individuals with a history of anaphylaxis to an injectable drug or vaccine containing polyethylene glycol or polysorbate—two components in authorized COVID-19 vaccines—should speak to an allergist before being vaccinated. 
• Patients with severe allergies to foods, oral drugs, latex, or venom can safely receive the COVID-19 vaccines.

“As allergists, we want to encourage vaccination by reassuring the public that both FDA-approved COVID-19 vaccines are safe,” study co-author Aleena Banerji, MD, clinical director of the Allergy and Clinical Immunology Unit at Massachusetts General Hospital, said in a statement. “Our guidelines are built upon the recommendations of U.S. regulatory agencies and provide clear steps to the medical community on how to safely administer both doses of the vaccine in individuals with allergic histories."

While the rare chance of an allergic reaction may mean a small subset of people can’t take the Pfizer or Moderna vaccines, other vaccines are coming up for review that may be safer for those at risk of anaphylaxis. 

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.