The Pfizer BioNtech COVID-19 Vaccine and the Moderna COVID-19 Vaccine are the two mRNA vaccines that have received emergency use authorization by the FDA and are being used at public vaccination sites. 

Some people (2 to 10 out of every million people vaccinated) have had severe allergic reactions to these vaccines. The majority of these reactions have occurred in individuals with an allergic background and a large number in individuals with a history of anaphylaxis.

We are conducting this study to determine whether patients who are Highly Allergic (HA) and/or are diagnosed with Mast Cell Disorder (MCD) experience allergic reactions at higher levels than other people. 

We think that the Pfizer and Moderna vaccines will be safe in the majority of HA and MCD individuals, but that there may be identifiable risk factors that can trigger allergic reactions in some individuals. If we are able to identify risk factors for allergic reaction to these vaccines, it could help physicians determine which vaccine is safest for HA and MCD patients. 

Learn more about the COVID Vaccine Allergy Study.