Vaccination

Vaccination is a preventative health measure that can confer immunity to an infectious disease, without requiring that the vaccinated individual actually contracts the disease. Usually, this is carried out with an innoculation, either a weakened form of the infectious agent (called a live vaccine) or a portion of the infectious agent, like an outer coat or internal proteins (called a killed vaccine) are introduced into the body of the individual to be protected. The immune system of that individual responds to the vaccine and, if that response is adequate, exposure to the germ will not result in sickness.