The side effects most associated with vaccines include pain, tenderness and redness at the injection site and underarm area, muscle aches, fatigue, fever, and headache. We expect vaccines for COVID19 to have similar side effects. A sore arm is the most commonly reported side effect from those who’ve received the vaccine so far. In a recent press release, Pfizer announced that most patients had mild to moderate symptoms, and the only severe reactions were fatigue, which happened to 3.8% of study participants, and headache, which affected 2% of study participants. The most common mild to moderate side effects for the Pfizer vaccine are pain, redness and swelling at the injection site, fatigue. Headache, muscle pain, chills, joint pain and fever. Patients in the Moderna vaccine clinical trial reported having pain at the injection site and underarm area, fatigue, muscle aches, joint pain, and headache. There have been a few reports of severe allergic reactions.
updated  12/30/20