Severe allergic reactions to COVID-19 vaccines are likely to be more common than severe reactions flu vaccines, but is still very rare according to a new report.
The authors of the report, of the Centers for Disease Control and Prevention (CDC), analyzed data from the first 1.9 million doses of COVID-19 vaccine administered in the US from December 14 to December 23. Most of this time, only the Pfizer-BioNTech COVID-19 vaccine was available in the US
The researchers identified 21 cases of people experiencing anaphylaxis – a potentially life-threatening allergic reaction – shortly after receiving the COVID-19 vaccine.
This is approximately 11 cases of anaphylaxis per 1 million doses of vaccine administered. In comparison, the rate of anaphylaxis after flu vaccination is 1.3 cases per million people, said Dr. Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases, said during a news conference on Wednesday (January 6).
Although the rate of anaphylaxis linked to COVID-19 vaccines is about ten times higher than that seen with flu vaccines, “it is still extremely rare,” Messonnier said. In general, the benefits of the vaccine outweigh the potential risks, she said.
Related: 7 strange signs that you have an allergic reaction
Of the 21 cases described in the report, 17 had a history of allergies or allergic reactions, including reactions to drugs, food, and insect stings; and seven of the people have experienced anaphylaxis in the past. Almost all of these patients were treated with epinephrine after their response to the COVID-19 vaccine, and all 21 recovered.
Although the new report only contains cases of Pfizer COVID-19 vaccine, the CDC is aware of confirmed cases of anaphylaxis that have also been linked to the Modern COVID-19 vaccine.
Exactly what causes these reactions is unclear, and ‘tremendous efforts’ are underway to better understand the cause, Messonnier said. One possible culprit is polyethylene glycol, an ingredient in both Pfizer and Moderna vaccines. Live Science reported earlier.
However, if you have allergies, you do not necessarily have a higher risk of reactions to COVID-19 vaccines. Allergies are common in the US, but serious reactions to the vaccines are not.
The CDC recommends that people with a history of reactions to vaccines or anaphylaxis for any reason should be observed by healthcare professionals for 30 minutes after receiving their COVID-19 shot. (In the report, patients experienced an average of about 13 minutes after their COVID-19 shot of anaphylaxis.)
The agency recommends that people not receive the Pfizer or Moderna vaccine if they have a known allergy to an ingredient in these vaccines, including polyethylene glycol; and people should not receive a second dose if they have a severe reaction to the first.
Originally published on Live Science.