Cowpox to the mild form of smallpox and the observation that dairy farmers were immune from smallpox inspired the first smallpox vaccine, created and administered by English physician Edward Jenner. The word “vaccination,” coined by Jenner in 1796, is derived from the Latin root "vaccinus", meaning of or from the cow. Once vaccinated, a patient develops antibodies that make them immune to cowpox, but they also develop immunity to the smallpox virus, or "Variola virus". The cowpox vaccinations and later incarnations proved so successful that in 1980, the World Health Organization announced that smallpox was the first disease to be eradicated
Smallpox the United States and South Africa a much milder form of smallpox, "variola minor", was recognized just before the close of the 19th century. By the mid-20th century "variola minor" occurred along with "variola major", in varying proportions, in many parts of Africa. Patients with "variola minor" experience only a mild systemic illness, are often ambulant throughout the course of the disease, and are therefore able to more easily spread disease. Infection with "v. minor" induces immunity against the more deadly "variola major" form. Thus as "v. minor" spread all over the USA, into Canada, the South American countries and