Vaccines
As early as 430BC, it was recognized that most individuals that survive a pustular epidemic are resistent to subsequent epidemics; see http://www.orion-group.net/Orion%20Medical/Journals/Vol6_May2000/24.htm.
Problems and aspects of inoculation are discussed at the following web site: http://www.909shot.com/PressReleases/prsmallpoxpolicy.htm .
The following web site describes a timeline of US National vaccination programs.
Visit this link frequently to learn more about various vaccines such as for the flu, anthrax, small pox, etc. and, especially, the origin of the word "various" itself as it relates to pustular diseases.