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A new study provides further evidence that anaphylaxis after COVID-19 vaccination is rare, occurring at a rate of 2.5 cases per million doses of Moderna’s vaccine.
The Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) analyzed data from the Vaccine Adverse Event Reporting System and confirmed 10 cases of anaphylaxis out of more than 4 million Moderna doses administered over three weeks, according to a new Morbidity and Mortality Weekly Report.
While monitoring will continue and advice may evolve, the CDC and FDA continue to support use of the vaccines.
“Widespread vaccination against COVID-19 with highly effective vaccines represents a critical tool in efforts to control the pandemic and save lives,” they wrote.
All 10 anaphylaxis cases in the report were females, although researchers noted more females than males were vaccinated. The median age was 47 years, and nine of the women had a history of allergies or allergic reactions to drugs, contrast media or food. The doses they received came from multiple lots of the vaccine, and there was no clustering in any one area of the country.
Symptoms occurred a median of 7.5 minutes after receiving the vaccine but ranged from one to 45 minutes. Six women were hospitalized, according to the report. Of those, five were treated in intensive care and four required endotracheal intubation. The remaining four women were treated in an emergency department. Researchers had follow-up information on eight of the women, all of whom have recovered or been discharged home. No deaths were reported.
A report earlier this month on the COVID-19 vaccine from Pfizer-BioNTech found an anaphylaxis rate of 11.1 cases per million doses. Like the Moderna cases, more females experienced reactions, most had a history of allergies or allergic reactions and symptoms typically began within minutes.
The CDC has emphasized the need for people administering vaccines to screen patients and to have the necessary supplies and training to recognize and treat anaphylaxis (see resources).
People should not receive a COVID-19 vaccine if they have a history of severe allergic reaction or an immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components, including polyethylene glycol. They also should not be vaccinated if they have a history of immediate allergic reaction of any severity to polysorbate.
People with a history of any immediate allergic reaction to any other vaccine or injectable therapy can receive the vaccine but should be counseled about the risks. Those with this history or a history of anaphylaxis due to any cause should be observed for 30 minutes after vaccination. All others should be observed for 15 minutes.