There are early reports of an allergic reaction to Pfizer's COVID-19 vaccine in health care workers across the world as the first groups of people are administered doses of the vaccine.  That has raised some questions by the general public. 

Danbury's Acting Health Director, Kara Prunty, says the U.S. Centers for Disease Control and Prevention and the Food and Drug Administration co-manage a program for vaccine safety.  The Vaccine Adverse Event Reporting System is used to collect any data on adverse events. 

She noted that there is a difference between a side effect and an adverse event.  A side effect is any health problem shown through studies, such as a fever, or unrelated health problems that occur whether the vaccine was administered or not.  An adverse event is a true reaction to the vaccine, such as common known effects and/or allergic reactions. 

Healthcare providers are required to report certain adverse events following the vaccine administration.