If you think correlation can be used as an argument you might want to check this:
Look at the life expectation and the rate of child mortality for developed countries from before vaccines started. (most of them will only show the rise AFTER vaccines started)
You will see it all started to rise before vaccinations started. Probably because the diseases knew the vaccines were coming?
No, probably because people were living in better conditions than before.
RE: A response to @chron: Why you should believe in Herd Immunity!