Onesimus
In 1721 Boston, an enslaved West African man taught the inoculation method that cut smallpox deaths from 14% to 2% — seventy-five years before Jenner's vaccine.
Onesimus — his birth name is lost — was a West African man, likely Akan from present-day Ghana, enslaved and given as a gift to the Boston minister Cotton Mather in 1706. Mather described him as “a pretty intelligent fellow.” Around 1716, Onesimus told Mather something remarkable: he could not catch smallpox, because he had undergone an operation in Africa — a small amount of smallpox material introduced through the skin — and showed Mather the scar on his arm.
The practice — variolation — was established medicine in parts of Africa long before Europeans understood it. When a smallpox epidemic tore through Boston in 1721, Mather cited Onesimus and African knowledge in urging doctors to inoculate. He was ridiculed for trusting the testimony of an enslaved man; opponents called African medicine a plot. One physician, Zabdiel Boylston, tried it anyway.
The results ended the argument: of 280 people inoculated during the epidemic, about 2.2 percent died — versus 14.3 percent of the nearly 6,000 who caught smallpox without it. The method spread through the colonies and preceded Edward Jenner's vaccine by 75 years. Onesimus, meanwhile, negotiated to buy his own freedom. In 2016, Boston magazine named him among the 100 Best Bostonians of all time.
Why You Should Know Them
American immunization has an African foundation stone. The knowledge that saved colonial Boston did not come from a European laboratory — it crossed the Atlantic in the memory of an enslaved man whom history nearly erased.