What’s causing allergic reactions to some COVID-19 vaccines? UNC working on an answer

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RALEIGH, N.C. (WNCN) – While very rare, allergic reactions to the Moderna and Pfizer vaccines are possible and have occurred. The reasoning behind it is still unclear even as more than six million vaccine doses have been administered in North Carolina.

“Overall, vaccines are safe. Any kind of reaction, for any kind of vaccine, tends to happen at a rate of one to a million. And that’s more or less what’s happened with reactions in general with the COVID-19 vaccine,” said Dr. David Peden at the UNC School of Medicine.

Peden and other doctors want to know why this is happening. UNC will join a national study is designed to examine allergies and the COVID-19 vaccines.

People in the study will get the Pfizer vaccine, Moderna vaccine, or placebo. Their possible reactions will be observed by allergy specialists. The person will then come back for their second dose for another observation.

Placebo recipients will eventually be offered a full vaccination as well.

Part of the study will look at how many people there are having a reaction. While reactions are submitted to federal reaction databases, following up on a large, general population is difficult. People can be hard to reach and investigators don’t have a full picture of the person’s condition prior to vaccination. That makes it hard to come up with definitive explanations for allergic reactions.

“We’re not just going to give them shots and watch to see what happens,” said Peden.

There will be blood work before and after a reaction. White blood cells will be looked at to examine why immune systems are reacting in a specific way.

“It’s not just important to know how often this occurs but it’s also important to understand why it might be occurring. So ultimately, we might identify before they get vaccinated to understand who might be at risk,” Peden said.

One-third of study volunteers will be non-allergy people so researchers can see if the rate reaction is really different between the two populations.

Click here to register for the study.

Click here to learn more about the study

Weighing the risks for allergic reactions

Ultimately, Peden hopes the study can also increase vaccine confidence for those who have been concerned about a potential reaction.

“If somebody has had a life threatening situation to a drug or to a food in the past- that experience for some people can be really, really unsettling,” he said.

Dr. Leonor Corsino receiving a COVID-19 vaccine. Courtesy: Duke Health

It’s how Duke Health endocrinologist, Dr. Leonor Corsino felt when she was offered the COVID-19 vaccine. She weighed the risk of a potential reaction and opted to get vaccinated.

“There have been some cases of allergic reactions but they’ve been small. That kind of made me more comfortable so on December 28, I received my first dose,” said Dr. Corsino.

Corsino said she’d had allergic reactions to foods and medications in the past.

“When you have anaphylaxis, it’s really scary. It’s not something you would recommend to anybody. In my case, it was really scary. I ended up in the emergency department,” said Corsino.

The doctor said she did her due diligence with reading CDC guidelines and recommendations. She also consulted with her healthcare provider. Ultimately, she said she chose to trust scientists behind the vaccine. She did not have a reaction to the vaccine.

How common are allergic reactions?

Initial analysis from the CDC found 2.5 cases of anaphylaxis per million doses of the Moderna COVID-19 vaccine.

They found 11.1 cases of anaphylaxis per million doses of the Pfizer COVID-19 vaccine.

For both vaccines, a majority of symptoms set in within 30 minutes of a person being vaccinated. Most of them also had a history of allergic reactions to foods, drugs, or bug bites, and most were women.

Peden’s study is hoping to get a better understanding of what those rates look like now.

CDC guidance

The following is guidance from the CDC for people with allergies.

If you are allergic to an ingredient in a COVID-19 vaccine

If you have had a severe allergic reaction or an immediate allergic reaction—even if it was not severe—to any ingredient in an mRNA COVID-19 vaccine, you should not get either of the currently available mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna).

If you have had a severe allergic reaction or an immediate allergic reaction to any ingredient in Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 vaccine, you should not get the J&J/Janssen vaccine.

If you aren’t able to get one type of COVID-19 vaccine because you are allergic to an ingredient in that vaccine, ask your doctor if you should get a different type of COVID-19 vaccine. Learn about the different types of COVID-19 vaccines.

If you had an allergic reaction to a previous shot of an mRNA vaccine

If you aren’t able to get the second shot of an mRNA vaccine because you had an allergic reaction to the first shot, ask your doctor if you should get a different type of COVID-19 vaccine. Learn about the different types of COVID-19 vaccines.

If you are allergic to polyethylene glycol (PEG) or polysorbate

PEG and polysorbate are closely related to each other. PEG is an ingredient in mRNA vaccines, and polysorbate is an ingredient in the J&J/Janssen vaccine.

If you are allergic to PEG, you should not get an mRNA COVID-19 vaccine. Ask your doctor if you can get the J&J/Janssen vaccine.

If you are allergic to polysorbate, you should not get the J&J/Janssen COVID-19 vaccine. Ask your doctor if you can get an mRNA COVID-19 vaccine.

If you are allergic to other types of vaccines

If you have had an immediate allergic reaction—even if it was not severe—to a vaccine or injectable therapy for another disease, ask your doctor if you should get a COVID-19 vaccine. Your doctor will help you decide if it is safe for you to get vaccinated.

If you have allergies not related to vaccines

CDC recommends that people get vaccinated even if they have a history of severe allergic reactions not related to vaccines or injectable medications—such as food, pet, venom, environmental, or latex allergies. People with a history of allergies to oral medications or a family history of severe allergic reactions may also get vaccinated.

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