How do COVID-19 vaccines work?
The vaccines work by teaching your body’s immune system to recognize the virus that causes COVID-19. This allows your body to fight off the virus if it ever encounters it. Vaccines can reduce the severity of disease if you become infected, and they can also help to prevent transmission of the virus to others.
Current evidence suggests that for most people, receiving two doses of the vaccine creates a strong enough immune response to effectively reduce the risk of developing COVID-19 or related serious illness. For people who don’t develop the same immune response to two doses of the vaccine, a third dose is needed to get a similar level of protection as other people. A third dose is not the same as a booster dose, which is an additional dose that “boosts” protection after the immune response from the initial two-dose vaccine decreases over time.