TAMPA, Fla. — The University of South Florida is one of only two sites in the state taking part in a National Institutes of Health study on whether people who are highly allergic or have a mast cell disorder are more likely to have allergic reactions to the Pfizer or Moderna vaccines.

“This is a study that was deemed high priority by NIH," said Dr. Thomas Casale, director of clinical and transitional research in allergy and immunology at USF.

"The public understandably has been concerned about reports of rare, severe allergic reactions to the Moderna and Pfizer-BioNTech COVID-19 vaccines," National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci is quoted as saying in a news release from the NIH. NIAID is part of NIH and also sponsoring and funding the study. "The information gathered during this trial will help doctors advise people who are highly allergic or who have a mast cell disorder about the risks and benefits of receiving these two vaccines. However, for most people, the benefits of COVID-19 vaccination far outweigh the risks."

Unlike the Johnson & Johnson vaccine, Pfizer and Moderna protect people against the virus using mRNA. Casale said it's unclear what it is about these formulas that have led to instances of allergic reactions.

“We know it’s not the mRNA - or almost definitely not the mRNA. What we think is it’s in the excipients, or the other components of the vaccine," said Casale. “It hasn’t been pinned down yet. So, part of the purpose of this study is that if we see acute allergic reactions, we will be drawing blood samples, genetic samples, et cetera, to try and elucidate exactly what is causing that allergic reaction.”

Casale said USF began enrolling patients for its branch of the study this week. Researchers plan to recruit 120 participants locally -- both those with and without histories of allergic reactions. 

“So, these would be people that have severe food allergies, who are allergic to bees, allergic to various drugs," said Casale.

Participants will be closely monitored for 90 minutes after receiving the vaccination. They'll be watched by doctors who have experience in identifying signs of allergic reactions.

“We would like to identify who’s at highest risk for these reactions, and then, if we could figure out why they’re at higher risk, then if there’s a next generation vaccine or a booster that comes out, they might be able to tweak it a bit so that it would lessen that possibility," Casale said.

To learn more about the study, including how to participate, visit the NIH Clinical Trials website.