Normally, when you are infected with a pathogen like a virus, your body responds with a series of reactions. When your body realizes there is an invader, an immune response occurs. This means that the body begins to produce proteins called antibodies that help to destroy the pathogens that can make you sick. After you are better, the antibodies stick around and are there to protect you against future infections. A vaccine works by injecting you with dead or inactive viruses so you will naturally produce antibodies and therefore protect you from future infection.
