Vaccination is the introduction into the human body weakened (or killed by Violent poison) pathogenic microbe.

If the Poison is not enough, the pathogenic microbes survives  in human body and leads to disease, from which patient been Immunized (Vaccinated).
If the Poison is enough, dead microorganisms generally (i.e. often, but not always) can induce immunity against this type of infection.
In any case, the human body gets a Poison that was used to kill pathogenic microbe.
While there were only few immunizations, the total amount of the poison generally did not result in severe disease up to 25 years. When the number of vaccinations has increased, the total amount of venom resulted poisoning from early childhood.

mandatory vaccination  & AIDS