Updated Jan. 7: The U.S. Centers for Disease Control and Prevention gave an update during a Jan. 6 press briefing on the incidence of severe reactions to the mRNA coronavirus vaccines.
There were 29 cases of anaphylaxis among the more than 5.3 million shots of the vaccine given as of Jan. 5, said Dr. Tom Clark, the CDC’s vaccination evaluation team leader.
That translates to a rate of 5.5 anaphylaxis cases per 1 million doses given at this stage of the vaccine program. While higher than the rate of anaphylaxis of 1.3 cases per 1 million shots with the flu vaccine, “I want to reassure you this is still a rare outcome,” said Dr. Nancy Messonnier, director of CDC’s National Center for Immunization and Respiratory Diseases. All patients were treated and recovered; there have been no deaths.
The agency and the U.S. Food and Drug Agency (FDA) are reviewing all reports of serious reaction reports to the Pfizer-BioNTech and Moderna mRNA vaccines submitted to the CDC’s vaccine events database. Of the 29 national cases of anaphylaxis to date, the agency has confirmed medical information with health-care providers on 21 cases.
Cause of Reactions Uncertain
At the press briefing, the CDC officials presented data from a report on the 21 confirmed cases, which occurred between Dec. 14 and Dec 23. Based on that earlier data, the rate of anaphylaxis was slightly higher – 11.1 per million doses given. The CDC report still characterizes this as a “rare event.”
Seventeen of the 21 patients had a history of allergies or allergic reactions to drugs or to foods or insect stings.
The CDC’s COVID-19 vaccine report says seven of these patients had experienced anaphylaxis in the past, including one to a rabies vaccine and one to a flu vaccine. Nineteen of the patients were reported as treated with epinephrine. The majority were women, and the median age of the 21 individuals was 40 years old.
Two allergy experts recently told Allergic Living that it is not known yet whether the the severe reactions to the mRNA vaccines are caused by an allergy to a vaccine component, noting that non-allergic immune system reactions can have very similar symptoms.
The New York Times reports that, as of Jan. 7, there were 21.4 million cases of COVID-19 virus in the United States and 361,000 lives lost to the virus. Messonnier emphasized the coronavirus toll and said: “The known and potential benefits of the current COVID-19 vaccines outweigh the known and potential risks of getting COVID-19.”
Clark added that “we know of many, many people with histories of allergies who are vaccinated uneventfully. So it’s a little bit difficult to interpret the frequency of allergies [to the vaccines] just in the cases.”
To gain more clarity, the National Institute of Allergy and Infectious Diseases (NIAID) is working with the CDC, the FDA and the mRNA vaccine makers on a study to see whether there truly is a higher incidence of reactions to the coronavirus shots among those with a history of severe allergies. Allergic Living has been told it will begin in February.
Safety Measures Stressed
Messonnier, the CDC official leading the coronavirus immunization effort, reiterated the safety recommendations for both mRNA vaccines. These include that “anyone with a history of an immediate allergic reaction to injectable vaccine and people with a history of anaphylaxis due to any cause, should be observed for 30 minutes.” As well, anyone who has an allergic reaction to the first shot of the two-dose mRNA vaccine regimen, should not have the second shot.
Most of the patients who had anaphylaxis began having symptoms within 15 minutes of getting the shot. Messonnier added that there were no geographic clusters of severe reactions.
“Fortunately, we know how to treat anaphylaxis, and we have put provisions in place to ensure that at immunization sites the folks administering the vaccine are ready to treat anaphylaxis,” she said.
“So the major message is, even if this rate of anaphylaxis is higher than what we see for routine immunizations, anaphylaxis after COVID-19 vaccination remains rare.”