Tracking serious COVID-19 vaccine reactions The U.S. CDC and the FDA use 'VAERS' to track adverse reactions. Patient submissions and evidence of some underreporting show it doesn't reveal a full picture. Author: Hannah Dineen (NEWS CENTER Maine) Published: 4:49 PM PST February 15, 2021 Updated: 8:14 AM PST February 16, 2021 BRUNSWICK, Maine — Since COVID-19 vaccinations first became available, the Center for Disease Control (CDC) warned the public about common side effects of the vaccine: soreness or swelling at the injection site-- or fever, chills, tiredness, and/or a headache in the days following vaccination. Occasionally, there are more serious reactions or "adverse reactions" to the vaccine. Federal authorities are tracking those reactions through an online database.