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National Jewish Health to Study Allergic Reactions to COVID-19 Vaccine


Researchers at National Jewish Health will determine if people who are highly allergic or have a mast-cell disorder are more likely than other people to have an allergic reaction to the Moderna or Pfizer-BioNTech COVID-19 vaccines. A mast-cell disorder is a buildup of white blood cells that release substances causing symptoms similar to an allergic reaction. The researchers will also study the biological mechanisms of any allergic reactions that do occur in vaccinated people.

National Jewish Health to Study Allergic Reactions to COVID-19 Vaccine

Although rare, serious allergic reactions have occurred in people who have received the Moderna and Pfizer-BioNTech vaccine. Most of the allergic reactions have occurred in women with a history of allergies.

The National Jewish Health team, led by Donald Leung, MD, PhD, and Flavia Hoyte, MD, will be one of 35 academic allergy-research centers across the nation enrolling participants in the Phase 2 trial, called Systemic Allergic Reactions to SARS-CoV-2 Vaccination, which is sponsored by the National Institute of Allergy and Infection Diseases.

“We want to understand who and why some people have developed severe allergic reactions to the Moderna and Pfizer-BioNTech COVID-19 vaccines,” said Dr. Leung.

Researchers are seeking participants 18 to 69 years of age who have not received a COVID-19 vaccine, those who have a history of serious allergic reactions or a mast cell disorder, as well as people who have no allergies at all. Participants will be assigned at random to receive either the Pfizer-BioNTech vaccine (one third of the group); the Moderna vaccine (one third); a placebo followed by the Pfizer-BioNTech vaccine (one sixth); or a placebo followed by the Moderna vaccine (one sixth). Initially, neither the participants nor the study team will know who is receiving a vaccine or placebo, or which vaccine is being administered. All participants ultimately will receive a full two-dose course of either the Pfizer-BioNTech vaccine or the Moderna vaccine.


National Jewish Health is the leading respiratory hospital in the nation. Founded 125 years ago as a nonprofit hospital, National Jewish Health today is the only facility in the world dedicated exclusively to groundbreaking medical research and treatment of children and adults with respiratory, cardiac, immune and related disorders. Patients and families come to National Jewish Health from around the world to receive cutting-edge, comprehensive, coordinated care. To learn more, visit the media resources page.

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