5 "Red Flags" After Your COVID Vaccine By Leah Groth of ETNT Health | 5 "Red Flags" After Your COVID Vaccine According to the Centers for Disease Control and Prevention as well as the Food and Drug Administration, all three of the COVID-19 vaccines—Moderna, Pfizer and Johnson & Johnson—are "safe and effective." However, side effects—the majority mild and temporary—are totally normal. There are also a few potential side effects that aren't so normal and can even be considered red flags. Read on to learn what they are—and to ensure your health and the health of others, don't miss these