The process of inoculation against diseases like smallpox has been known for at least 1200 years. An 8th-century Indian book contains a how-to chapter on smallpox inoculations. Chinese use of the technique dates back to the first millennium as well. The technique was imported to Europe via the Ottoman Empire in 1721 and reached America at about the same time.
The practice is documented in America as early as 1721, when Zabdiel Boylston, at the urging of Cotton Mather, successfully inoculated two slaves and his own son. Mather, a prominent Boston minister, had heard a description of the African practice of inoculation from his Sudanese slave, Onesimus, in 1706, but had been previously unable to convince local physicians to attempt the procedure. Following this initial success, Boylston began performing inoculations throughout Boston, despite much controversy and at least one attempt upon his life. The effectiveness of the procedure was proven when, of the nearly three hundred people Boylston inoculated during the outbreak, only six died, whereas the mortality rate among those who contracted the disease naturally was one in six.