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Onesimus: The enslaved black man who shaped American inoculation

Photo of Onesimus
Photo of Onesimus

With vaccines being at the forefront of our fight to end the COVID-19 pandemic, the importance of inoculation weighs heavy on our minds. But did you know that the practice of vaccinations in America can be traced all the way back to the 1700s (nearly a century before Edward Jenner developed what would become known as the modern-day smallpox vaccine) when an enslaved man named Onesimus changed the course of history?

While there are a few versions of this important moment in medical history, all accounts tell the story of a Libyan-born slave named Onesimus being sold to Puritan Boston minister, Cotton Mather. Mather notices that Onesimus and many other slaves all bear a similar scar on their arms. When he inquires about the scar, Onesimus tells Mather that in Africa, they would take pus from the wounds of an individual infected with smallpox and insert it into a cut made on a healthy person. While not 100% effective, this would typically cause a mild reaction and resulted in some degree of smallpox immunity for the healthy individual.

Several accounts recall that Mather was “conflicted” on how trustworthy Onesimus truly was, however, he ultimately shared this information with a local white physician named Zabdiel Boylston. Boylston tried the technique on several people, including his own son, and was pleased to discover the procedure was largely successful. He ends up using this practice (called “variolation”) and saving hundreds upon hundreds of lives in the area. Mather and Boylston were hailed as heroes, while Onesimus is all but erased from this incredibly important milestone in medicine. And despite his life-saving contribution to the smallpox outbreak, he was still not a free man.

Onesimus and countless other individuals were unjustly stripped of their rightful recognition as vital contributors to science and medicine, among other disciplines. While nothing can undo the damage done by such cruel omissions from defining moments in history, we must do our part to acknowledge their innumerable contributions to humanity by continuing to share important stories like that of Onesimus.