INOCULATION WAS INTRODUCED TO AMERICA BY A SLAVE

In 1721, Boston experienced its worst outbreak of smallpox (also known as variola). 5,759 people out of around 10,600 in Boston were infected and 844 were recorded to have died between April 1721 and February 1722.

Cotton Mather, a preacher and slave owner, claimed to be in possession of a way of actually preventing contraction of the disease that he had learned from one of his former slaves. A decade earlier, Mather’s congregation had purchased for him an African slave whom Mather named Onesimus, after a slave in the Bible whose name meant “useful or profitable.” 

Like most slaves, Onesimus's name at birth and place of birth are not known with certainty, he was first documented as living in the colonies in 1706, and having been brought to North America as a slave. He is recorded as having described himself as Guramantese, it is unclear what ethnic group exactly this refers to but most accounts place him among the Coromantee from the coastal areas of modern-day Ghana.

Mather educated him in reading and writing with the Mather family and in 1716 or shortly before, Onesimus had described to Mather the process of inoculation that had been performed on him and others in his society in Africa.

Enquiring of my man Onesimus, who is a pretty Intelligent Fellow, Whether he ever had the Small-Pox; he answered, both, Yes, and No; and then told me, that he had undergone an Operation, which had given him something of the Small-Pox, and would forever preserve him from it, adding that it was often used among the Guramantese, & whoever had the Courage to use it, was forever free from the Fear of the Contagion. He described the Operation to me, and showed me in his Arm the Scar. 

Mather, in a 1716 letter to the Royal Society of London, on his introduction to inoculation from Onesimus.

Cotton Mather

What Onesimus was describing to Mather was the variolation method of inoculation was long practiced in Africa among sub-Saharan people. With material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result . The procedure was most commonly carried out by inserting/rubbing powdered smallpox scabs or fluid from pustules into superficial scratches made in the skin. The patient would develop pustules identical to those caused by naturally occurring smallpox, usually producing a less severe disease than naturally acquired smallpox. Eventually, after about two to four weeks, these symptoms would subside, indicating successful recovery and immunity.

Mather followed Onesimus's medicinal advice and worked with a physician, Dr. Zabdiel Boylston, to carry out the method Onesimus had described, which involved sticking a needle into a pustule from an infected person's body and scraping the infected needle across a healthy person's skin.  Dr. Boylston first inoculated his 6-year-old son and two of his slaves. A total of 280 individuals were inoculated during the 1721-22 Boston smallpox epidemic. The population of 280 inoculated patients experienced only 6 deaths (approx. 2.2 percent), compared to 844 deaths among the 5,889 non-inoculated smallpox patients (approx. 14.3 percent).

This became the earliest experiment with public inoculation. Their efforts would inspire further use and research of variolation for immunizing people from smallpox, placing the Massachusetts Bay Colony at the epicenter of the Colonies' first inoculation debate and profoundly impacting Western society's medical treatment of the disease. After Mather and Boylston's highly-publicised experiments with inoculation, and Lady Mary Wortley Montagu's similar experiments during a simultaneous outbreak in London, variolation would become a widespread and well-researched technique in the West decades before Edward Jenner's discovery of vaccination with cowpox.

In 1980, the World Health Organization declared that smallpox had been completely eradicated due to global immunization efforts, making the disease the first and only infectious disease have been entirely wiped out. 

In a 2016 Boston Magazine survey, Onesimus was declared number 52 on a list of the "Best Bostonians of All Time"