An analysis of allergic reactions to the first 17.5 million COVID-19 vaccines given in the U.S. has found 66 confirmed cases of anaphylaxis. Almost all the severe reactions occurred in women, and most were in people with a history of allergies or anaphylaxis, according to a study led by researchers at the U.S. Centers for Disease Control and Prevention (CDC).
Yet people with allergies should take comfort that the rate of anaphylaxis is very low – 4.7 cases for every one million people who receive the Pfizer-BioNTech vaccine, and 2.5 cases per one million Moderna shots, says Dr. Tom Shimabukuro, deputy director of the CDC’s Immunization Safety Office and an author of the study.
With few exceptions, the CDC advises that anyone with a history of food, medication or insect sting allergies should get the vaccine as soon as they are eligible. “Anaphylaxis is a rare event, and COVID-19 is a serious disease that can cause a lot of harm, especially in susceptible individuals,” Shimabukuro told Allergic Living. “The bottom line is the benefits of preventing disease and death from COVID-19 disease far outweighs the risk of any adverse events from these vaccines.”
The study, published online in the Journal of the American Medical Association (JAMA) on Feb. 12, analyzed reports of reactions to the Vaccine Adverse Event Reporting System (VAERS) between Dec. 14 and Jan. 18.
During that time period, nearly 10 million Pfizer mRNA vaccines and 7.6 million Moderna shots were administered across the United States. CDC researchers identified 47 reports of anaphylaxis following the Pfizer vaccine, and 19 following the Moderna vaccine.
Among the Pfizer vaccine anaphylactic reactions, 94 percent were in women, as were 100 percent of the Moderna vaccine anaphylaxis cases. Anaphylaxis is a severe allergic reaction that can occur soon after vaccination, often starting within 30 minutes.
Three-quarters of the 66 who experienced anaphylaxis to the mRNA vaccines had a history of allergies. About 32 percent of them (21 people) had a history of anaphylaxis. Individuals reported prior anaphylaxis to a wide range of triggers including: other vaccines (rabies and flu), medication (sulfa drugs and penicillin), foods like nuts, as well as latex, jellyfish stings and to contrast media used during medical imaging scans.
The CDC does advise people with a history of severe food, drug, pet, venom or latex allergies to get the mRNA vaccines. The exception is for individuals who have an allergy polyethylene glycol (PEG) or polysorbate, since those are contained in the shots. The CDC also recommends people who’ve had an allergic reaction to another vaccine or injectable medication to discuss vaccination with their allergist first.
Patterns of Vaccine Reactions
VAERS is a vaccine safety surveillance system that collects reports of adverse health events after vaccinations from the public and healthcare personnel. With the new COVID-19 inoculations, the most common types of adverse events reported tend to be milder post-vaccine side effects, such as headache, fatigue and dizziness, which are not allergy based.
It’s still early days for the new RNA vaccines. Since not much is yet known about what caused the small number of severe reactions, “it’s difficult to draw conclusions about specific patterns or risk factors in the individuals reporting these events,” Shimabukuro says. “However, there is a relatively high proportion of those who experience anaphylaxis after vaccination who have a history of allergies or allergic reactions,” he says.
As for the gender split, women made up about 60 percent of those who received the vaccine during the early rollout, which could help to explain why they accounted for more cases of anaphylaxis than men.
Yet previous research shows that women are also more likely to have serious allergic reactions to other types of vaccines, including flu shots. Of 350 cases of anaphylaxis in adults following an influenza or other vaccine reported to VAERS between 1990 and 2016, about 80 percent occurred in women. (However in that research, of 479 reports of anaphylaxis in children following a vaccine, 65 percent were boys).
Despite more side effects being seen with second doses of the mRNA vaccines, most of the 66 anaphylactic reactions occurred in response to the first dose. Both the Pfizer and the Moderna vaccine require two doses, spaced several weeks apart.
Although some experts have suggested that an allergy to an ingredient in the vaccines – polyethelyene glycol or polysorbate – could be behind some of the cases of anaphylaxis, none of the 66 had a known allergy to either substance. This is not surprising, Shimabukuro says, as PEG allergies are rare and anyone who has one may have avoided the shot.
Everyone who had anaphylaxis after the COVID-19 vaccines recovered. Nearly all received epinephrine. About half were hospitalized, including 18 in intensive care. Symptoms of anaphylaxis included hives, swelling, difficulty breathing and nausea.
Bigger Side Effects Picture
In other research, the CDC’s Morbidity and Mortality Weekly Report, gave a fuller accounting of all of the adverse events submitted to VAERS during the first month of the vaccine rollout. From Dec. 14 to Jan. 13, there were about 13.8 million vaccines administered, and nearly 7,000 reports of adverse events – or 0.05 percent of all patients given the vaccine. (This includes most of the anaphylaxis cases captured in the JAMA study).
Shimabukuro noted that reports of adverse reactions do not necessarily mean the vaccine caused it. “Some may be true adverse reactions to the vaccine, some may be coincidental health events that may not be related to the vaccine at all,” he says. “VAERS is not designed to determine cause and effect. It’s designed to pick up unusual or unexpected patterns that might indicate a potential safety issue.”
The CDC advises that any facility administering COVID-19 vaccines should have trained medical personnel, supplies and equipment to manage anaphylaxis. Those with a history of severe allergic reactions to any cause should be observed for at least 30 minutes after vaccination. All others are to be monitored for at least 15 minutes.
“Anaphylaxis is a clinically serious event, but anaphylaxis is treatable,” says Shimabukuro.
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