When questions come up about illnesses that might be vaccine related, they are investigated and the public is given detailed information about the risks of taking the vaccine compared to the risks of getting COVID-19.
The most common side effects are similar to the ones many people have from other vaccines: pain or tenderness at the site of the shot and tiredness and flu-like symptoms about a day later.
Some people have developed severe allergic reactions after getting a Covid-19 vaccine. These reactions are rare (less than 5 per million). For your safety, you will be asked about your history of allergy before you are given a vaccine and you will be observed for up to 30 minutes afterward to be sure you are okay. In the unlikely event that you do have a reaction, emergency medical providers will be on site to treat you immediately.
So far, no other serious side effects have been definitively linked to the Pfizer or Moderna mRNA vaccines.
A small number of children and adolescents who got Pfizer or Moderna vaccines have developed inflammations of the heart. This condition is very rare and is still under investigation, but it does not appear to be more common in vaccinated people. Blood clots have been found in some women under age 50 who were given the Johnson & Johnson vaccine. The risk of developing this condition as a result of Covid is greater than the risk associated with vaccination, but in the interest of safety we no longer recommend the Johnson & Johnson vaccine for women younger 50.