Erased: Onesimus and the Origins of American Inoculation

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Erased

An African Man Taught America Inoculation — Decades Before The First Vaccine.

Learning Objectives

By the end of this lesson, students will be able to:

  • Identify Onesimus and describe his role in introducing variolation to colonial Boston
  • Explain the practice of variolation and how it differs from Edward Jenner's later smallpox vaccine
  • Describe Cotton Mather's response to learning about African inoculation practices and his effort to convince Boston's physicians to adopt them
  • Analyze Zabdiel Boylston's decision to test variolation on his own family before treating hundreds of additional patients
  • Explain how variolation was used during the Revolutionary War and its impact on the Continental Army
  • Evaluate why Onesimus was largely denied credit for his contribution to American medicine while Boylston and Jenner were remembered

Key Vocabulary

  • Onesimus — An enslaved African man in colonial Boston, purchased by the Puritan minister Cotton Mather in 1706. Onesimus told Mather that a method of protecting against smallpox was practiced in his homeland, describing a scar on his own arm as proof. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[7]Massachusetts Historical Society. Cotton Mather Papers and Diary documentation.
  • Variolation — The practice of deliberately introducing a small amount of live smallpox virus into a healthy person's body, typically through a scratch or incision in the skin, so the body could develop immunity without suffering the full, often fatal, natural infection. Those who survived variolation became immune for life. [2]Mather, Cotton. An Account of the Method and Success of Inoculating the Small-Pox in Boston in New-England. London, 1722.[4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.
  • Cotton Mather — A Puritan minister in colonial Boston who learned of variolation from Onesimus and other enslaved Africans. Mather spent years urging Boston's physicians to adopt the practice, facing significant public resistance and hostility. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[2]Mather, Cotton. An Account of the Method and Success of Inoculating the Small-Pox in Boston in New-England. London, 1722.
  • Zabdiel Boylston — The only Boston physician who acted on Mather's urging during the 1721 smallpox epidemic. Boylston tested variolation on his own family before treating hundreds of additional patients, producing results that were later credited with legitimizing the practice in the American colonies. [3]Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.[4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.
  • Smallpox — A highly contagious and frequently fatal viral disease that caused recurring epidemics in colonial America and Europe, with mortality rates as high as 30 percent among the naturally infected. [4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.[8]World Health Organization. "History of Smallpox Vaccination." who.int historical archive.
  • The 1721 Boston Smallpox Epidemic — A severe outbreak of smallpox that struck Boston in 1721, killing hundreds of residents and prompting Cotton Mather's urgent push for the city's doctors to adopt variolation. [4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.[6]Fenn, Elizabeth A. Pox Americana: The Great Smallpox Epidemic of 1775–82. New York: Hill and Wang, 2001.
  • Continental Army Inoculation — In 1777, General George Washington ordered the mass inoculation of Continental Army soldiers against smallpox, using the same variolation principle first described to Cotton Mather decades earlier. Disease had threatened to disable the army more severely than combat itself. [6]Fenn, Elizabeth A. Pox Americana: The Great Smallpox Epidemic of 1775–82. New York: Hill and Wang, 2001.
  • Edward Jenner and the First Vaccine — An English physician who, in 1796, developed a smallpox vaccine using cowpox material rather than live smallpox virus. Jenner's method built on the same underlying principle behind variolation and became known as the first true vaccine. [8]World Health Organization. "History of Smallpox Vaccination." who.int historical archive.
  • West African Medical Tradition — A body of practiced medical knowledge, including variolation, documented among healers across parts of West Africa for generations before European colonists learned of it. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[5]Miller, Genevieve. The Adoption of Inoculation for Smallpox in England and France. Philadelphia: University of Pennsylvania Press, 1957.
  • Scarification — The physical technique used in variolation, in which a small incision or scratch was made in the skin to introduce infectious material from a smallpox patient into a healthy individual. [2]Mather, Cotton. An Account of the Method and Success of Inoculating the Small-Pox in Boston in New-England. London, 1722.[3]Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.

The Full Lesson

Part 1 — The Question That Changed History

In 1706, a man named Onesimus arrived in Boston in chains, purchased by the Puritan minister Cotton Mather. His freedom was taken. His knowledge was not. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[7]Massachusetts Historical Society. Cotton Mather Papers and Diary documentation.

One day, Mather asked Onesimus a simple question: had he ever had smallpox? Onesimus answered, "yes and no." Then he rolled up his sleeve and showed Mather a scar — evidence of a practice that had protected him from the disease that was, at that very time, one of the deadliest threats in the colonial world. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[2]Mather, Cotton. An Account of the Method and Success of Inoculating the Small-Pox in Boston in New-England. London, 1722.

"Yes. And no."

Part 2 — Medicine, Not Magic

Back in Africa, healers had protected people from smallpox before the disease could kill them. They voluntarily introduced a small amount of the virus into the body — a practice called variolation — so it could learn to fight back and become immune for life. [2]Mather, Cotton. An Account of the Method and Success of Inoculating the Small-Pox in Boston in New-England. London, 1722.[4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.

This wasn't magic. It wasn't luck. It was medicine — medicine that had been practiced across parts of West Africa for generations. Mather didn't simply take Onesimus at his word. He asked other enslaved Africans in Boston, and they all described the same practice. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[7]Massachusetts Historical Society. Cotton Mather Papers and Diary documentation.

"It wasn't magic. It wasn't luck. It was medicine."

A West African healer performing scarification inoculation on a patient's arm
A healer performs scarification inoculation — a practice passed down through generations in West Africa.

Part 3 — Boston Runs Out of Time

In 1721, Boston ran out of time. Smallpox spread through the city. Families watched loved ones die. Doctors had no answer. Mather begged Boston's physicians to try what Onesimus had taught him. Only one doctor listened: Zabdiel Boylston. [3]Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.[4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.[6]Fenn, Elizabeth A. Pox Americana: The Great Smallpox Epidemic of 1775–82. New York: Hill and Wang, 2001.

"Doctors had no answer."

Part 4 — Trusting African Medical Knowledge

Boylston trusted the knowledge that had originated with Onesimus and tested it on his own family first. Then he treated hundreds more patients, and the results changed American medicine forever. The numbers were impossible to ignore — the evidence supported Onesimus. [3]Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.[4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.

Boston still refused to give him credit. But truth has a way of surviving. The practice spread beyond Boston, colony after colony, as more physicians began using a medical practice they had once rejected. [3]Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.[5]Miller, Genevieve. The Adoption of Inoculation for Smallpox in England and France. Philadelphia: University of Pennsylvania Press, 1957.

"The evidence supported Onesimus. Boston still refused to give him credit."

A colonial physician examining a patient's inoculation scars, with an African man standing unacknowledged in the background
Boylston tests variolation on a patient in colonial Boston — knowledge that originated with Onesimus, standing unacknowledged nearby.

Part 5 — From Colonial Boston to the Continental Army

Decades later, disease threatened the Continental Army more severely than British bullets. In 1777, General George Washington ordered thousands of soldiers to be inoculated — using the same principle Onesimus had described to Cotton Mather more than seventy years earlier. [6]Fenn, Elizabeth A. Pox Americana: The Great Smallpox Epidemic of 1775–82. New York: Hill and Wang, 2001.

"Washington ordered thousands of soldiers to be inoculated."

Part 6 — The Knowledge Came From Africa. The Credit Did Not.

In 1796, Edward Jenner built on the same underlying principle to create the first vaccine, using cowpox instead of live smallpox virus. [8]World Health Organization. "History of Smallpox Vaccination." who.int historical archive.

History remembered Jenner. History remembered Boylston. But the African man who introduced inoculation to America in the first place — Onesimus — was almost forgotten. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[7]Massachusetts Historical Society. Cotton Mather Papers and Diary documentation.[8]World Health Organization. "History of Smallpox Vaccination." who.int historical archive.

"The knowledge came from Africa. The credit did not."

Critical Thinking Discussion Questions

  1. Onesimus answered Cotton Mather's question about smallpox with "yes and no," then showed him a scar. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011. What does this response reveal about how enslaved Africans navigated moments of being asked to share knowledge with those who enslaved them?
  2. Zabdiel Boylston tested variolation on his own family before treating hundreds of others. [3]Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.[4]Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974. What does this decision suggest about the risk he was willing to take on knowledge that originated with an enslaved African man?
  3. Despite the evidence supporting Onesimus's knowledge, Boston refused to credit him. [3]Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.[5]Miller, Genevieve. The Adoption of Inoculation for Smallpox in England and France. Philadelphia: University of Pennsylvania Press, 1957. What does this reveal about how credit and authorship were assigned in colonial science?
  4. George Washington ordered thousands of Continental Army soldiers to be inoculated using the same method Onesimus described. [6]Fenn, Elizabeth A. Pox Americana: The Great Smallpox Epidemic of 1775–82. New York: Hill and Wang, 2001. Why do you think this practical, life-or-death decision didn't extend to acknowledging its African origins?
  5. History remembers Edward Jenner and Zabdiel Boylston, but Onesimus was nearly forgotten. [1]Best, Michael. "Note: Cotton Mather, Onesimus, and the Origins of Inoculation." Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.[8]World Health Organization. "History of Smallpox Vaccination." who.int historical archive. What does this pattern reveal about whose contributions get preserved in historical memory, and whose get erased?
A timeline illustration showing an African healer on one side and colonial physicians examining a vaccine vial on the other
The knowledge came from Africa. The credit did not.

Quiz — Erased: Onesimus and the Origins of American Inoculation

Part A: Select the best answer and check your work instantly. Part B: Write in complete sentences.

Part A — Multiple Choice

1. In what year did Onesimus arrive in Boston in chains?

2. What question did Cotton Mather ask Onesimus that changed history?

3. What is variolation?

4. Who was the only Boston physician who listened to Mather and tested variolation?

5. What did Boylston do before treating hundreds of patients with variolation?

6. Decades after Onesimus described variolation, what did Edward Jenner create using a similar principle?

7. What pattern does this lesson argue is revealed by history remembering Jenner and Boylston but nearly forgetting Onesimus?

Part B — Short Answer

8. Onesimus told Cotton Mather "yes and no" when asked if he had ever had smallpox, then showed him a scar. Using details from the lesson, explain what this exchange reveals and why it mattered.

9. Explain the practice of variolation in your own words, including where it originated and how it worked.

10. The lesson argues "The knowledge came from Africa. The credit did not." Using at least two specific examples, explain what evidence supports this claim.

Extension Activity

Trace the Origin: Research one additional historical example of medical or scientific knowledge that originated in Africa or with enslaved or colonized peoples and was later credited primarily to a European or American figure. Describe: (1) the original source of the knowledge, (2) who received credit, and (3) how the true origin was documented or rediscovered. Then write two to three sentences connecting your example to the pattern described in this lesson.

Sources & Footnotes

  1. [1] Best, Michael. Note: Cotton Mather, Onesimus, and the Origins of Inoculation. Journal of the History of Medicine and Allied Sciences, vol. 66, no. 4, 2011.
  2. [2] Mather, Cotton. An Account of the Method and Success of Inoculating the Small-Pox in Boston in New-England. London, 1722.
  3. [3] Boylston, Zabdiel. An Historical Account of the Small-Pox Inoculated in New England. London, 1726.
  4. [4] Winslow, Ola Elizabeth. A Destroying Angel: The Conquest of Smallpox in Colonial Boston. Boston: Houghton Mifflin, 1974.
  5. [5] Miller, Genevieve. The Adoption of Inoculation for Smallpox in England and France. Philadelphia: University of Pennsylvania Press, 1957.
  6. [6] Fenn, Elizabeth A. Pox Americana: The Great Smallpox Epidemic of 1775–82. New York: Hill and Wang, 2001.
  7. [7] Massachusetts Historical Society. Cotton Mather Papers and Diary documentation.
  8. [8] World Health Organization. History of Smallpox Vaccination. who.int historical archive.

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