1. Vaccine is an injection, usually of an innocuous (weak or killed) form of the virus, that stimulates the production of antibodies by the immune system to help prevent or create resistance to an infection.
Notes: Vaccines are usually given as a preventive measure.
2. A preparation consisting of antigens of a disease-causing organism which, when introduced into the body, stimulates the production of specific antibodies or altered cells. This produces an immunity to the disease-causing organism. The antigen in the preparation can be whole disease-causing organisms (killed or weakened) or parts of these organisms.