Side effects vary depending on the individual and the vaccine. Many people may have mild side effects. The most common include pain or redness at the site of the injection, fatigue, headache, muscle ache, fever, and chills. Most let up within a day. Clinical trials of both the Pfizer and Moderna vaccines had low numbers of people experiencing severe side effects. You can read more about reported side-effects of the Johnson & Johnson vaccine here.
Check out the Centers for Disease Control and Prevention (CDC) website for more details.
Researchers will continuously follow vaccinated people for the appearance of any long-term side effects. There are multiple vaccine safety systems in place in the United States for all vaccines. These systems will be used to monitor the safety of Covid-19 vaccines.