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College of Medicine, Hershey Medical Center join clinical trial evaluating allergic reactions to COVID-19 vaccines

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Researchers at Penn State College of Medicine are participating in a national clinical trial evaluating whether people who have previously experienced severe allergic reactions are at increased risk for an immediate, systemic allergic reaction to the Moderna or Pfizer-BioNTech COVID-19 vaccines. The College of Medicine is the only site in Pennsylvania participating in the study, which is funded by the National Institute of Allergy and Infectious Diseases.

According to the Centers for Disease Control and Prevention (CDC), anaphylaxis, a severe allergic reaction, after COVID-19 vaccination is rare and occurs in approximately two to five people per million vaccinated in the United States. In this study, patients will receive a full two-dose course of either the Pfizer-BioNTech or Moderna vaccines and be observed for 90 minutes with a doctor and emergency equipment present in case a patient has an allergic reaction or other adverse effect.

The researchers will determine whether systemic allergic reactions — which occur in one or more parts of the body beyond the injection site — occur more frequently in participants who are highly allergic or have a mast cell disorder than in participants without these diseases. A mast cell disorder is a disease where people become predisposed to life-threatening reactions that look like allergic reactions caused when a type of white blood cell (mast cell) becomes abnormal, overly active or both. The researchers will also examine the biological mechanisms behind the reactions and whether a genetic pattern or other factors can predict who is at the highest risk.

“Reports of rare, severe allergic reactions to COVID-19 vaccines have caused concern, particularly among patients with a history of severe allergic reactions,” said Dr. Timothy Craig, professor of medicine and pediatrics and an allergy, asthma and immunology specialist at Penn State Health Milton S. Hershey Medical Center. “This research will help doctors advise their patients who are highly allergic or who have mast cell disorders about the risks and benefits of receiving either the Moderna or Pfizer-BioNTech vaccines and any COVID-19 booster shots that may be needed in the future. For most people, the benefits of COVID-19 vaccination far outweigh the risks.”

The Moderna and Pfizer-BioNTech COVID-19 vaccines are the first two COVID-19 vaccines authorized by the Food and Drug Administration for emergency use and already have been given to millions of Americans. Most of the rare, severe allergic reactions to these vaccines have occurred in people with a history of allergies. Many of these people had previously experienced a life-threatening allergic reaction called anaphylaxis.

The trial will enroll 3,400 adults ages 18 to 69 years at up to 29 academic allergy research centers nationwide. Craig plans to enroll more than 100 participants to the study, which has recruited six participants so far. Participation is optional and compensation and travel reimbursement are provided.

More than half of the study participants must have a history of severe allergic reactions related to food food, insect stings, allergen immunotherapy, vaccines or drugs within the past five years. The remaining participants cannot have a history of such allergic reactions or mast cell disorders.

Participants in each group will be assigned at random to receive either the Pfizer-BioNTech vaccine, the Moderna vaccine or a placebo followed by the Pfizer-BioNTech or Moderna vaccines. 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.

Craig and other members of the research team will closely monitor participants’ safety throughout the trial and are trained to recognize and treat anaphylaxis. Emergency medications, oxygen and medical equipment will be on hand to treat allergic reactions as needed. Participants will be observed for at least 90 minutes after each injection in case any type of reaction occurs. The researchers will assess participants’ health during follow-up calls, the last of which will happen seven days after their last dose.

For more information on the trial visit StudyFinder, call 717-531-4513 or go to and search NCT04761822.

Read more about the clinical trial in this National Institute of Allergy and Infectious Diseases news story.

This research is supported by the National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

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