Why COVID-19 Vaccine Side Effects May Feel Worse After the Second Dose

All vaccines could cause some degree of reaction, and the same is true for COVID-19 vaccines. Post-vaccine symptoms are typically mild and resolve quickly without the need to use any medication. Common COVID-19 vaccine side effects include: Redness or soreness at injection site. Muscle aches. Fatigue. Headache. Fever or chills. For some people, the second dose in a COVID-19 vaccine series is causing a stronger reaction and more side effects than the initial dose. The same was true during clinical trials.