CDC: Anaphylaxis rate with COVID Vax 10 times higher than for flu shots

While rare, the anaphylaxis rate appeared about 10 times higher after COVID-19 mRNA vaccines than with flu shots, CDC officials said Wednesday.

A total of 21 cases of anaphylaxis after COVID vaccination were reported out of approximately 1.9 million doses given on December 23, according to an early Weekly report on morbidity and mortality release. That works out to 11.1 cases per million, versus an estimated 1.3 cases per million as a result of inactivated flu vaccine, agency officials said during a media appeal.

They noted that as of now, 29 confirmed cases of anaphylaxis have been reported with the Pfizer / BioNTech and Moderna vaccines. In addition, officials said, the MMWR Dec. 14-23 report focuses on the Pfizer vaccine, as the Moderna vaccine wasn’t available until Dec. 21. Still, there is not enough data to show a difference in risk between vaccines.

No deaths from anaphylaxis have been observed to date.

Nancy Messonnier, MD, director of CDC’s National Center for Immunization and Respiratory Diseases, stressed that these events were rare and the benefits of COVID-19 vaccination outweighed the risks. Additionally, comparing these to the flu figures “misses the point” when there are more than 2,000 deaths from COVID-19 in the US every day.

“It is still a valuable proposition,” she said. “Even if the rate is higher than what we see after routine immunizations, anaphylaxis remains rare.”

Out of 21 cases assessed in MMWR18 had documented allergies or allergic reactions to medicines, medical products, food, or insect stings, and seven had had anaphylaxis in the past, including one after a rabies vaccine and one after an influenza A (H1N1) vaccine.

Messonnier acknowledged the millions of people who are allergic to food or insect stings, highlighting the difference between “someone who had a mild allergic reaction in childhood and someone who had a severe allergic reaction next week.”

“Many people have a history of allergy to bee sting or food and the fact that people in this group had anaphylaxis … may not mean that allergic reactions put them at higher risk, but it could be,” she added.

Messonnier noted that CDC guidelines state that anyone with a history of anaphylaxis for any reason should talk to their healthcare provider prior to vaccination and that clinicians should exercise their judgment.

CDC officials said anyone with a history of anaphylaxis who gets the vaccine should be observed for 30 minutes afterward, as people who previously had anaphylaxis are at risk of getting it again.

The agency recently updated its interim guidelines for clinicians on contraindications to the vaccine, adding that those with an immediate allergic reaction to the first vaccine should not receive a second dose.

Seventeen of the 21 cases were among those with a history of anaphylaxis and the median time from vaccination to symptom onset was 13 minutes, although about 70% of patients showed symptoms within 15 minutes. The median age of the patients was 40 and 19 were women.

The MMWR report noted that female predominance had previously been seen for immediate hypersensitivity reactions to influenza A (H1N1) vaccine. But the disproportionality with COVID vaccination may simply be due to the fact that more women than men are getting the Pfizer / BioNTech vaccine, the authors said.

Nineteen patients were treated with epinephrine, 17 were treated in the emergency department and four were hospitalized, including three in intensive care. Of the 20 with available information, all were fired home.

Messonnier also briefly addressed reports from health professionals who chose not to be vaccinated, saying she was “definitely” concerned about it.

“It makes it extremely important that we get the right information to health professionals and that we get rid of wrong information quickly,” she said. “We need them not only to protect themselves, but to educate their patients so that everyone understands these vaccines … have a good safety profile, they work, and they … can help us end this pandemic. “