African variolation (Onesimus's testimony)

What it is

Onesimus told Cotton Mather that in Africa he had been inoculated with smallpox pus for protection, a practice other Africans in Boston confirmed. His testimony prompted the 1721 Boston inoculation campaign, one of the earliest statistical tests of a medical procedure.

Mather reported it to the Royal Society in 1716. Onesimus's exact origin is uncertain (he is often identified with the Coromantee of the Gold Coast, but this is undocumented). Variolation was also practised in China, India and the Ottoman Empire.

What it led to

• Zabdiel Boylston's inoculation campaign in Boston (1721)
• the numerical comparison of mortality between inoculated and non-inoculated people
• acceptance of inoculation in the British colonies

Made possible

• Variolation (smallpox inoculation)1721
• Smallpox vaccine1796
• Smallpox vaccine

Links

Sources✓ verified 2026-09-23

• https://en.wikipedia.org/wiki/Onesimus_(Bostonian)
• https://www.paulreverehouse.org/onesimus-mather-and-the-origins-of-inoculation-in-boston/