Images Narayan Nair, M.D.

The details of the first severe allergic reactions (anaphylaxis) tied to Pfizer-BioNTech COVID-19 vaccine inoculations have been released by federal health agencies.

Between Dec. 14 and 23, the Centers of Disease Control and Prevention identified 21 validated case reports of anaphylaxis among 1.9 million first doses of the vaccine. This amount corresponds to a rate of approximately 11 cases per one million doses, investigators reported. 

Among the 21 patients who experienced anaphylaxis, the medium time from vaccination to symptom onset was 13 minutes, and 18 patients had onset within 30 minutes. Common signs of allergic reaction were hives (urticaria); rapid edema, or swelling beneath the skin; rash; and a feeling of throat closure, reported Narayan Nair, M.D., an epidemiologist with the Food and Drug Administration, and colleagues.

Approximately 80% of these patients had a history of allergies or allergic reactions. These histories included reactions to drugs or medical products, food and insect stings. Fully 33% had experienced a past episode of anaphylaxis, including one after receiving a rabies vaccine and another after receiving the influenza A(H1N1) vaccine.

In addition:

  • 19% were hospitalized (including 3 in intensive care)
  • 81% were treated in an emergency department 
  • 95% are known to have been discharged home or had recovered at the time of the report to the Vaccine Adverse Event Reporting System
  • No deaths from anaphylaxis were reported

Milder reactions

During the same vaccination period, 83 cases of non-anaphylaxis allergic reactions to the vaccine were identified. The most common of these milder reactions included itching (pruritus), rash, itchy and scratchy sensations in the throat, and mild respiratory symptoms, the researchers wrote.

The report, published Thursday in JAMA Network, also includes a summary of the CDC’s guidance on the use of mRNA COVID-19 vaccines and the management of anaphylaxis.