[chimeracoder]

> polio and smallpox were eradicated

FYI, polio has not been eradicated. It's been eliminated from all but eight countries, and is endemic on only two of those. But it has not yet been eradicated.

> I am 45 years old and never had a smallpox or polio vaccine, so that makes me an anti-vaxxer regarding those two, yet here we are and I don't see those diseases making big comebacks?

Well, don't travel to Afghanistan or Pakistan.

More seriously: you can't contract polio without being exposed to it[1]. There is no poliovirus in the US (outside laboratory settings), so you wouldn't have had the chance to contract it.

That state (the situation in which there is no poliovirus in the US) would not have been achieved without the vaccine, though, so you are still benefiting from the vaccine's use.

[1] whether in the wild or in vaccine-derived cases