Vaccines work by introducing a weakened or inactive form of a virus or bacteria into the body. This allows the body to recognize the virus or bacteria and create antibodies to fight it. If the body is exposed to the virus or bacteria in the future, the antibodies will be ready to fight it, preventing the body from becoming infected. Vaccines are an effective way to prevent disease, as they can help to reduce the risk of infection and reduce the severity of symptoms if the body does become infected.