The first evidence of successful variolation was found in a Chinese manuscript from 1549. Variolation was the process of taking a small amount of smallpox material and introducing it to a person, hoping that only a mild infection would occur. This practice was done in China, India, the Horn of Africa, Turkey and other parts of the Ottoman Empire. Lady Mary Wortley Montagu, wife to the British ambassador to Turkey, wrote back to her friend in England about the smallpox variolation in Turkey. Upon her return to England in 1718 and a later smallpox outbreak in 1721, Lady Montagu was instrumental in smallpox variolation gaining traction in England and the approval of the British monarchy.
A smallpox outbreak also hit the American colonies in 1721. Cotton Mather, a Boston minister, learned of smallpox variolation from his slave, Onesimus, who had been variolated in Africa as a child. He encouraged this practice in Boston, but was met with resistance. The later Revolutionary War, 1775 to 1783, allowed for more wide scale acceptance and use of variolation. George Washington went against the Continental Congress and argued that smallpox posed a threat to military operations and variolation should be mandatory for soldiers. By 1778, the smallpox death rate among soldiers dropped from 17% to 1%. This was the first instance of mandatory inoculation in the United States.
Davidson, Tish. Vaccines: History, Science, and Issues. Santa Barbara, CA: Greenwood, 2017.
Feemster, Kristen A.. Vaccines: What Everyone Needs to Know. Oxford: Oxford University Press, 2017.