Most adults are no longer immunised against "childhood" diseases

In most adults
their childhood vaccines have worn off
Because they don't deliver natural lifelong immunity
Like actual illnesses generally do.

This means that aiming for 100% vaccination rates in children,
By overriding questioning parent's free will,
Seems a little odd

 If a much larger group of adults
  are walking around
Effectively unvaccinated,

And presenting the same "risk" factor
  to a non-immune child.