Onesimus was an enslaved African who, in the late 17th century, was purchased and given as a gift to Puritan minister Cotton Mather. His extensive knowledge of inoculation, a practice he had undergone in Africa to prevent smallpox, would later prove invaluable during a time when the smallpox epidemic threatened to decimate the population of Boston.
Born in West Africa, Onesimus was kidnapped and forcibly brought to the shores of America. He was first documented as living in the colonies in 1706, having been brought to North America as an enslaved person. In December of that same year, a church congregation contributed money to purchase him and presented him as a gift to Cotton Mather, their Puritan minister of North Church.
Under Mather’s ownership, Onesimus was given a new name and soon played an important role in introducing an innovative method of disease prevention to the New World.
In 1716 or earlier, Onesimus recounted to Mather a procedure he had undergone in Africa known as variolation—a method of inoculation against smallpox. This operation involved introducing a small amount of the smallpox virus into the body to induce immunity. With Onesimus’s guidance, Mather learned of this technique, laying the groundwork for its adoption in the American colonies.
When smallpox reared its deadly head in Boston in 1721, Mather, armed with Onesimus’s knowledge, championed the use of inoculation to curb its spread. However, his advocacy faced staunch opposition from those skeptical of African medicine and wary of interfering with divine providence. Also, Mather was ridiculed publicly for relying on the testimony of an enslaved person. But despite the ridicule and resistance from city officials, Mather persevered, spurred by Onesimus’s insights.
Dr. Zabdiel Boylston, inspired by Onesimus’s teachings, undertook the risky task of inoculating Bostonians. By introducing the virus to healthy individuals, he sought to build immunity and stem the epidemic. The results were remarkable: of the 280 individuals inoculated, only six succumbed to the disease—a stark contrast to the staggering mortality rate among the non-inoculated population. This practice eventually spread to other colonies.
An inscription on Dr. Zabdiel Boylston tomb incorrectly identifies Boylston as the “first” to have introduced the practice of inoculation into America.
In 1796, Edward Jenner replaced the inoculation method introduced by Onesimus with his development of vaccination for smallpox and cowpox. Subsequently, vaccination became mandatory in Wales and England, while variolation was prohibited due to its side effects. In 1980, the World Health Organization declared smallpox completely eradicated thanks to global immunization efforts, marking it as the first and only human infectious disease to achieve such a feat.
Onesimus’s contribution to medical science and public health was not fully recognized until centuries later. In 2016, Boston magazine honored him as one of the “Best Bostonians of All Time,” acknowledging the important role he played in shaping the city’s history.
Beyond his contributions to public health, Onesimus’s personal struggles reflect the complexities of enslaved life in colonial America. Despite earning independent wages and providing for his household, including his wife and two children who tragically passed away before reaching the age of ten, he remained bound to the Mather household.
The details of Onesimus’s later life and his eventual fate remain a mystery. No records exist to confirm when he passed away, leaving his story unfinished.
