How do vaccines work?

The COVID-19 vaccines work by helping your body develop protection against COVID-19. Different types of vaccines work in different ways to offer protection. When your immune system is exposed to the vaccine, it produces antibodies (proteins in the blood) that will remember how to fight the actual virus if you ever become exposed to it in the future. This prevents you from getting sick.

Both the Pfizer-BioNTech and Moderna COVID-19 vaccines are messenger RNA (mRNA) vaccines. These vaccines tell your cells to make a harmless protein—the same one found on the virus that causes COVID-19. Your immune system then responds by making antibodies against this protein. Your body will remember how to fight this protein if you’re ever exposed to COVID-19 in the future.

Johnson & Johnson’s Janssen vaccine is a viral vector vaccine.Viral vector vaccines use a harmless virus that’s different from the one that causes COVID-19. When the vaccine enters the body, the virus works with the body to create a protein that is found on the virus that causes COVID-19. This triggers the immune system to make antibodies against COVID-19 to protect against future infection.

The Novavax vaccine makes a protein that precisely mimics the protein found on the COVID-19 virus. Learning to recognize this protein helps your immune system protect you from getting seriously sick from COVID-19.