US Starts Study of Allergic Reactions to Moderna, Pfizer COVID-19 Vaccines

A nurse fills up a syringe with the Moderna COVID-19 vaccine at a vaccination site at a senior center in San Antonio, Texas, on March 29, 2021. Sergio Flores/Getty Images

A U.S. health agency on April 7 announced the launch of a study of allergic reactions to two COVID-19 vaccines.

The phase two trial will examine whether people with a history of allergic reactions or who have a mast cell disorder are at increased risk of an immediate, systemic allergic reaction to the vaccines made by Moderna and Pfizer-BioNTech.