SAN FRANCISCO (KPIX) – This week, health care workers begin sitting down to get their second dose of the COVID-19 Pfizer vaccine. Before the booster shots are administered, the vaccinators ask the patient if they had any severe side effects.
The concern is over anaphylaxis: a severe, potentially life-threatening allergic reaction. It is known to occur rarely after vaccination.

Now, when it comes to the COVID-19 vaccines, the Centers for Disease Control published a new anaphylaxis study in the agency’s Morbidity and Mortality Weekly Report.

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“It may be more common that what we see typically with other vaccines,” said U.C Berkeley infectious disease expert Dr. John Swartzberg.

In the first week-and-a-half of the vaccine’s rollout, researchers detected 21 cases of anaphylaxis after nearly 2 million doses. That’s about 11 cases per million. It is still rare but, the flu shot is more like 1 case per million doses.

In this study, more women than men had a reaction, including rashes, wheezing, and trouble breathing. Some were treated with epinephine. A small number needed hospitalization.

“I think the risk of the virus far exceeds the risk of anaphylaxis to me,” said Menlo Park dentist Dr. Scott Hoffman

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These cases occurred with both the Pfizer and Moderna vaccines. More were seen with Pfizer but researchers believe that’s because the Pfizer vaccine was released before the Moderna vaccine.

Most of the anaphylaxis cases were seen in individuals who had a history of allergic reactions to certain foods like nuts or shellfish, some medications and bug bites.

“It does raise a red flag or at least an orange flag that people with allergies may need to be a little more careful,” noted Dr. Swartzberg.

Most reactions occur with 15 minutes of vaccination. The CDC recommends anyone who gets a COVID-19 vaccine remain on site for observation for 15 minutes. If you have a history of allergic reactions, you should remain for at least 30 minutes, or longer, if you feel more comfortable.

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The CDC’s Dr. Nancy Messonnier told reporters Wednesday that the vaccine is still considered very safe, and that the risk of getting COVID-19 far outweighs the very small risk of a rare anaphylactic reaction.

Elizabeth Cook