Why vaccinate?

In a large study of more than a million Swedish children's medical records:

Psychosis risk was almost tripled by childhood mumps exposure and was over 16 times as high after cytomegalovirus exposure.

Childhood mumps risk can be virtually eliminated with vaccination. Cytomegalovirus is a common and often mild form of herpes.

The study is one of the first to show a link between an infectious disease and a mental illness (in this case schizophrenia). Schizophrenia, of course, has strong genetic links as well, but viral infections of the central nervous system may be an alternate or triggering factor in the manifestation of the mental illness.