Why is it that we do not become ill once we are vaccinated?

Each time we overcome infection, our bodies are left with a special system of defence against the germs which caused our illness. So, if we get the same infection again, our bodies are ready to fight it with the antibodies it has produced. Vaccination is based on this reaction. A human body is injected with a weak form of infection by dead or weak germs, and this is enough to produce the antibodies necassary to fight it