Excerpts from Books and Wikipedia
By 1800, smallpox vaccination was being practiced all over Europe. [Furtado: 1001 Days] "The smallpox vaccine was the first vaccine to be developed against a contagious disease. In 1796, the British doctor Edward Jenner demonstrated that an infection with the relatively mild cowpox virus conferred immunity against the deadly smallpox virus. Cowpox served as a natural vaccine until the modern smallpox vaccine emerged in the 20th century. From 1958 to 1977, the World Health Organization conducted a global vaccination campaign that eradicated smallpox, making it the only human disease to be eradicated. . . . A method of inducing immunity known as inoculation, insufflation or "variolation" was practiced before the development of a modern vaccine and likely occurred in Africa and China well before the practice arrived in Europe." [Wikipedia: Smallpox vaccine]