This Europe in the 18th Century. Smallpox is everywhere, 400,000 Europeans are dying from it each year. And there's no cure, but there might be hope... there's a doctor who thinks he's found a way to fight the disease. All you need to do is let him infect you with some good, old-fashioned, cowpox-infected pus. Of course, there is this other doctor who says, "Sure, you could do that, but it will might make your face look like a cow's." And the debate over vaccines began.
BBC: Edward Jenner (1749 - 1823)
World Health Organization: Frequently asked questions and answers on smallpox
Health Affairs: The History Of Vaccines And Immunization: Familiar Patterns, New Challenges