"By the late 1700s, Edward Jenner observed that milkmaids and others previously infected with cowpox were immune to smallpox. Cowpox caused lesions similar to smallpox, but the lesions were localized, and the disease was much milder and not considered deadly. Building on the world and observations of other physicians at the time, Jenner devised a series of experiments in which a person who had not previously acquired smallpox nor cowpox would be inoculated first with cowpox and later with smallpox. The gambit paid off. The subjects of these experiments showed a mild reaction to cowpox, and no reaction nor disease to smallpox inoculation. The first vaccine was born. For almost eighty years, cowpox vaccination against smallpox remained the only vaccine in use around the world. Science and technology were not yet there to create vaccines against other disease-causing organisms, though many tried."