How many cases did the U.S. have when the smallpox was around? Polio? The population was much less back then. But life goes on.
Not only was the population much less back then, but also consider this. An early 1900s Supreme Court case, possibly the first case of its kind, was decided in favor of smallpox vaccination after more than 100 years of use of vaccine after it initially produced desired results in late 1700s.
Also, emphasizing that I'm not medically trained, I keep wondering if fighting some diseases would have been more successful if vitamin D3 had been discovered before vaccines.
Corrections, insights welcome.