NIH researchers to study allergic reactions to COVID-19 mRNA vaccine

Key points to remember

  • The NIH has launched a clinical trial designed to help understand rare but potentially serious systemic allergic reactions to COVID-19 mRNA vaccines.
  • The trial is important because people who have had a reaction may be reluctant to complete the recommended series of vaccines or receive a booster in the future.
  • Researchers also hope to understand whether anxiety can trigger certain reactions to vaccines.

Serious allergic reactions are rare, regardless of the type of vaccine. But health authorities are taking steps to understand allergic reactions to the Pfizer or Moderna COVID-19 mRNA vaccine to allay concerns for those who might be hesitant to get a second or third shot.

The National Institute of Allergy and Infectious Diseases (NIAID) in March launched a clinical trial which recruits participants who have had an allergic reaction to the first dose of mRNA vaccines.

The 100 study participants between the ages of 16 and 69 will receive a second supervised dose of the vaccine, along with a placebo the next day, while being monitored for any reactions.

“People who have had an allergic reaction after receiving a COVID-19 mRNA vaccine may be reluctant to complete their treatment regimen,” Anthony S. Fauci, MD, NIAID Director and Chief Medical Advisor to the President, said in a report. “This study will help us determine if people who have experienced mild systemic allergic reactions can safely receive a second dose of a COVID-19 mRNA vaccine.”

Pamela A. Guerrerio, MD, PhD, head of the NIAID Allergic Diseases Laboratory and lead of the trial, mentioned that life-threatening allergic reactions to mRNA vaccines are extremely rare – only about five cases per million doses administered.

For people who have had a severe or immediate allergic reaction to the Pfizer or Moderna COVID-19 vaccine, the Johnson & Johnson vaccine is recommended instead, according to the Centers for Disease Control and Prevention (CDC).

Guerrerio told Verywell that allergic reactions were closely monitored during the early days of the COVID-19 vaccination campaign. But those reactions were rare, at two to five incidents per million doses, she said.

More women than men showed allergies to the COVID vaccine, according to Guerrerio. “We have not yet been able to identify specific indications of risk, which is why the trial is so important,” she said.

She added that most people who had a mild to moderate allergic reaction to the first dose will be able to tolerate the second dose. And some took antihistamines before their second dose to reduce potential allergy symptoms.

Another option is to receive the same vaccine but under an allergist’s care, especially if they’ve had some type of life-threatening reaction, such as difficulty breathing, Guerrerio said. Allergists usually give a small dose and wait 15-30 minutes before continuing with a slightly larger dose, with emergency medication on hand.

What counts as a severe allergic reaction?

An allergic reaction is considered serious when a person needs to be treated with epinephrine or EpiPen or if the person needs to go to the hospital. Severe allergic reactions are called anaphylaxis, which can also be triggered by foods, insect bites, medications, and latex.

In addition to monitoring patient reactions to second doses and placebos, researchers will also conduct immunological studies to learn more about the mechanisms behind the reactions. They will examine whether anxiety also affects the outcome of allergic reactions.

Allergic reactions to mRNA vaccines are likely caused by allergic antibodies called immunoglobulin E (IgE), which are responsible for the symptoms of an allergic reaction, Guerrerio said.

What is immunoglobulin E (IgE)?

IgE is an antibody response produced naturally by B cells secreted by the lymph nodes. This antibody normally activates physical responses to help your body fight infections. For some people, exposure to harmless allergens, such as dust or pollen, can also trigger the body to produce and release IgE.

mRNA vaccines are also the first vaccines to contain a component called polyethylene glycol (PEG), thought to be responsible for allergic reactions. However, there have been very few documented cases of severe allergic reaction to PEG following COVID-19 vaccination. In a rare case, British researchers have suggested screening patients who may have an allergy to PEG with a skin test before vaccination.

Guerrerio pointed out that the current data is extraordinarily clear that the vaccine is a very effective strategy to prevent severe COVID-19. “So even if people have had any reaction to the first dose of vaccine, it’s critical that they talk to their providers about ways to be fully immunized with the second dose and boosters.” she says.

The NIH researchers hope to complete their study by the end of 2022.

What this means for you

Serious allergic reactions to vaccines are rare. If you receive a COVID-19 vaccine and you have immediate reactions such as difficulty breathing, swelling of your tongue or throat, alert the provider immediately. If you have a reaction such as hives, swelling, and wheezing within four hours of vaccination, get medical help right away by calling 911.

The information in this article is current as of the date indicated, which means that more recent information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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