Unfortunately, I see no group immunity. I see immune-compromised people who suffer permanently from damage. I had pretty much all childhood diseases, and while they were inconvenient, I came away with absolutely no damage. Nor do I know anyone who died of any childhood disease.

A GP's income is considerably improved when he gives vaccinations. I wouldn't bite the hand that feeds me either. :)

There is an interesting bit on polio history here (http://www.marytocco.com/polio.htm).