When we think of the history of vaccines, names like Edward Jenner and Louis Pasteur often come to mind. But the roots of vaccination reach back further to an enslaved African man named Onesimus, whose knowledge helped Boston fight one of the deadliest diseases in history: smallpox.

In 1721, long before modern immunology existed, Onesimus shared a traditional African practice that would shape the future of global medicine. His insight came at a time of desperation and fear, and it ultimately saved countless lives. Despite living in bondage, Onesimus made a contribution to public health that is only recently being fully recognized.

Smallpox: A Deadly Threat in the Colonies

Smallpox was one of the most feared diseases of the 17th and 18th centuries. Highly contagious and often fatal, it left survivors with deep scars or blindness. Outbreaks were common and devastating, especially in cities like Boston where dense populations and poor sanitation helped the disease spread rapidly.

In 1721, Boston was hit by a particularly severe smallpox epidemic. Hundreds of people died, and panic swept through the population. Doctors and ministers searched for solutions, but effective treatments were almost nonexistent.

It was in this moment that Onesimus’s voice changed the course of history.

A Practice from Africa

Onesimus was enslaved by Cotton Mather, a Puritan minister and prominent figure in colonial Boston. When asked about whether he had ever had smallpox, Onesimus reportedly replied that he had undergone a procedure in Africa that prevented him from catching the disease.

He described a method in which material from a smallpox sore was introduced into the skin of a healthy person. The person would usually develop a mild case and then become immune. This process known as inoculation or variolation was already used in parts of Africa, Asia, and the Middle East.

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Onesimus and the Smallpox Epidemic of 1721

Mather was intrigued and began advocating for the practice, though he faced strong opposition from many in the medical community and general public. Critics feared the procedure could worsen the outbreak or spread disease further. Others simply refused to believe that medical knowledge could come from an African source, especially from an enslaved man.

Trial and Triumph

Despite the controversy, Mather convinced Dr. Zabdiel Boylston to begin inoculating volunteers. Boylston inoculated over 200 people in Boston during the epidemic. While some developed symptoms, the death rate among the inoculated was significantly lower than among those who contracted the disease naturally.

Of those who received the treatment, only a small percentage died compared to nearly one in six among the general population. This early success marked a turning point in the perception of inoculation and paved the way for later advancements in vaccination.

A Legacy Nearly Forgotten

Although Edward Jenner would later develop the modern smallpox vaccine in 1796 using cowpox, Onesimus’s story reminds us that the concept of disease prevention through exposure was not new. His contribution predates Jenner’s work by over 70 years.

Yet for centuries, Onesimus’s role in the history of vaccination went largely unrecognized. Only recently have historians begun to re-examine his story and acknowledge how African medical knowledge helped shape Western medicine.

His story is not just about science. It’s also about resilience, cross-cultural knowledge sharing, and the power of unheard voices.

Video:

Why Vaccines Work

Remembering Onesimus Today

Today, Onesimus is finally gaining the recognition he deserves. In 2006, he was named by The Boston Globe as one of the most influential Bostonians of all time. His story is now taught in some medical and historical education programs as a powerful reminder that innovation often comes from unexpected places.

As the world continues to rely on vaccines to combat diseases like COVID-19, Onesimus’s legacy feels more relevant than ever. His knowledge, courage, and cultural roots remind us that global medicine has always been deeply interconnected.