- The NIH launched a clinical trial designed to help understand rare but potentially severe systemic allergic reactions to COVID-19 mRNA vaccines.
- The trial is important because people who have experienced a reaction may be reluctant to complete the recommended vaccine series or get a booster in the future.
- Researchers also hope to understand if anxiety can trigger some reactions to the vaccines.
Severe allergic reaction is rare in any type of vaccine. However, health authorities are taking steps to understand allergic reactions to the Pfizer or Moderna COVID-19 mRNA vaccine to ease the concerns of those who may be reluctant to get their second or third shot.
National Institute of Allergy and Infectious Diseases (NIAID) in March launched a clinical trial it is to recruit participants who 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 monitored second-dose vaccine as well as a placebo the following day, while being monitored for any reactions.
“People who experienced an allergic reaction after receiving a COVID-19 mRNA vaccine may be reluctant to complete their vaccine regimen,” Anthony S. Fauci, MD, NIAID director and chief medical adviser to the president, said in a statement. “This study will help us determine if individuals who experienced moderate systemic allergic reactions can safely receive a second dose of a COVID-19 mRNA vaccine.”
Pamela A. Guerrerio, MD, PhD, head of NIAID’s Laboratory of Allergic Diseases and head of the trial, said that life-threatening allergic reactions to mRNA vaccines are extremely rare – only about five cases per one million administered doses.
For individuals who had a severe or immediate allergic reaction to either 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 in the early days of the COVID-19 vaccination campaign. But these reactions turned out to be rare, at two to five events per million doses, she said.
More women than men have shown COVID vaccine allergy, according to Guerrerio. “We have not yet been able to identify any specific indications of risk, and that is why the trial is so important,” she said.
She added that most people who have had a mild to moderate allergic reaction to the first dose will be able to tolerate the second dose. And some have taken antihistamine before their second dose to reduce potential allergy symptoms.
Another option is to receive the same vaccine, but under treatment by an allergy sufferer, especially if they had a life-threatening type of reaction, such as difficulty breathing, Guerrerio said. Allergists typically give a small dose and wait 15 to 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 to be serious when a person is to be treated with epinephrine or EpiPen, or when the person is going to the hospital. Severe allergic reactions are called anaphylaxiswhich can also be triggered by food, insect bites, medications and latex.
In addition to monitoring patients’ reactions to the second dose and placebo, researchers will also conduct immunological studies to learn more about the mechanisms behind the reactions. They will investigate whether anxiety also affects the outcome of allergic reactions.
Allergic reactions to the mRNA vaccines are presumably 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 naturally produced by B cells secreted by lymph nodes. This antibody usually activates physical reactions to help your body fight infections. For some people, exposure to harmless allergens, such as dust or pollen, can also cause the body to produce and release IgE.
The mRNA vaccines are also the first vaccines to contain a component called polyethylene glycol (PEG), which was thought to be responsible for the 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 suggested screening patients who may have pre-existing PEG allergies with a skin prick test before vaccination.
Guerrerio stressed that the current data are extraordinarily clear that the vaccine is a very effective strategy to prevent severe COVID-19. “So even though people had some kind of reaction to the first dose of vaccine, it’s crucial that they talk to their providers about ways to get fully vaccinated with the second dose and boosters.” she said.
NIH researchers hope to have their study completed by the end of 2022.
What this means for you
Severe allergic reactions to vaccines are rare. If you receive a COVID-19 vaccine and have immediate reactions such as difficulty breathing, swelling of your tongue or throat, you should alert your provider immediately. If you have a reaction such as hives, swelling and wheezing within four hours of vaccination, seek immediate medical attention by calling 911.
The information in this article is current from the date stated, which means that more recent information may be available as you read this. For the latest updates on COVID-19, visit our coronavirus news site.