Study to evaluate allergic reactions to COVID-19 vaccines in people with severe allergies

April 8, 2021

A clinical trial is underway to determine whether people who are highly allergic or have a mast cell disorder are at increased risk for an immediate, systemic allergic reaction to the Moderna or Pfizer-BioNTech COVID-19 vaccines, according to a news release from the National Institutes of Health (NIH).

If such an allergic reaction occurs in study participants, investigators will assess whether the reactions are more frequent in participants who are highly allergic or have a mast cell disorder than in participants with no allergic history. In addition, investigators will examine the biological mechanism behind the reactions and whether a genetic pattern or other factors can predict who is at most risk.

A mast cell disorder is a disease caused by a type of white blood cell called a mast cell that is abnormal, overly active, or both, predisposing a person to life-threatening reactions that look like allergic reactions.

The Phase 2 trial, called Systemic Allergic Reactions to SARS-CoV-2 Vaccination, is sponsored and funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of NIH. The vaccines are being provided by the program led by the U.S. Department of Health and Human Services and the U.S. Department of Defense to develop COVID-19 vaccines and therapeutics.

The study team will enroll 3,400 adults ages 18 to 69 years at up to 35 academic allergy-research centers nationwide. About 60% of study participants, group 1, must have either a history of severe allergic reactions or a diagnosis of a mast cell disorder, while 40% of participants, group 2, will not.

The specific types of allergic reactions in group 1 participants are related to food, insect stings or allergen immunotherapy and require treatment with a drug called epinephrine; or are immediate allergic reactions to a vaccine or to one or more drugs. These reactions will have occurred within the past 5 years. Group 2 will consist of people with no history of any allergic reactions or allergic disease and no history of a mast cell disorder. Approximately two-thirds of participants in each group will be female, because severe allergic reactions to vaccines in general – and to the Moderna and Pfizer-BioNTech COVID-19 vaccines in particular – have occurred mainly in women.

Investigators will assess the proportion of study participants in each group who have a systemic allergic reaction within 90 minutes after injection with either dose of the Pfizer-BioNTech vaccine or either dose of the Moderna vaccine. Results are expected in late summer 2021.

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