All of the authorized vaccines work by helping your body produce antibodies. Antibodies are proteins that help fight infections from viruses, bacteria and other germs. Mild symptoms are common as when the body produces antibodies, and are not a sign of infection.
In ongoing clinical trials, the most common side effects included:
- Pain at the injection site
- Fatigue
- Headache
- Muscle pain
- Chills
- Joint pain
- Mild fever
Side effects are generally mild and went away after a day or two. For the Pfizer and Moderna vaccines, they are likely to be more pronounced after the second shot.
A few people who have received the Johnson & Johnson vaccine experienced rare blood clots along with a low level of platelets within two weeks of their vaccination. The incidence of this side effect is about 1 in 1 million. If you receive the Johnson & Johnson vaccine and experience any sign of a blood clot or low platelets, including severe headaches, abdominal pain, leg pain, shortness of breath, or easy bruising or tiny blood spots under the skin beyond the site of injection, contact your doctor or seek medical care immediately.
As with any vaccine, there is a low chance of allergic reaction. If you have a history of severe allergic reaction to other vaccines, please talk to your doctor about whether you should receive the COVID-19 vaccine.