Onesimus  

Cotton Mather was a puritan minister in New England, he was an author and known for his vigorous involvement in the Salem Witch Trials, I only mention him as he relates to the slave he owned named Onesimus. Mather named him after a biblical slave who escaped from his master, an early Christian named Philemon. Onesimus, was born in the late seventeenth century, probably in Africa, although the precise date and place of his birth are unknown.

In the 17th century smallpox had become a serious threat in colonial New England decimating the population, at this time it had been managed by quarantine, incoming ships that came into the Boston harbor were quarantined  and the patients in town were housed in pesthouses. Smallpox was highly contageous and the mortality rate was as high as 30%.

Onesimus showed Mather his smallpox scar and told him: 

"you. take the Juice of the Small Pox, and Cut the Skin and put in a drop: then by 'nd by a little Sick, then a few Small Pox; and no body dye of it; no body have Small Pox any more." Mathers said, He told him that it was often used among Africans. In 1721, five years later, Mather used the information to inoculate people during a smallpox epidemic in Boston.

*cited~excerpt from an  article: http://hutchinscenter.fas.harvard.edu/

Reports of similar practices in Turkey further persuaded Mather to mount a public inoculation campaign. Most white doctors rejected this process of deliberately infecting a person with smallpox--now called variolation--in part because of their misgivings about African medical knowledge. Public and medical opinion in Boston was strongly against both Mather and Dr. Zabdiel Boylston, the only doctor in town willing to perform inoculations; one opponent even threw a grenade into Mather’s home. A survey of the nearly six thousand people who contracted smallpox between 1721 and 1723 found, however, that Onesimus, Mather, and Boylston had been right. Only 2 percent of the six hundred Bostonians inoculated against smallpox died, while 14 percent of those who caught the disease but were not inoculated succumbed to the illness.

It is unclear when or how Onesimus died, but his legacy is unambiguous. His knowledge of variolation gives the lie to one justification for enslaving Africans, namely, white Europeans’ alleged superiority in medicine, science, and technology. This bias made the smallpox epidemic of 1721 more deadly than it need have been. Bostonians and other Americans nonetheless adopted the African practice of inoculation in future smallpox outbreaks, and variolation remained the most effective means of treating the disease until the development of vaccination by Edward Jenner in 1796.