Covid-19 vaccine side effects

Vaccinations for Covid-19 are now underway in the U.S. Two vaccines – one from Pfizer and BioNTech, one from Moderna — have received emergency use authorizations by the Food and Drug Administration. Both vaccines have been deemed safe, but they can cause some short-term side effects. Vaccines are designed to invoke an immune response that builds protection without causing a serious infection. Traditionally, vaccines are made with viral material which prompts the immune system to mount a defense. This process releases chemicals that cause physical symptoms — such as pyrogens, which are inflammatory chemicals that can cause fever.