The Slave and the Milkmaid
from the book, "Petrified Lightning"

Petrified Lightning

The Slave and the Milkmaid

For many centuries a dreaded infectious disease called smallpox ravaged Europe and America. Each epidemic killed about 40 percent of those who contracted the disease, which permanently disfigured all its victims. Now, in the final decades of the 20th century, smallpox no longer presents a threat. For the discovery of that medical milestone, civilization is indebted to an African slave in Boston who belonged to Cotton Mather.

Mather (1663—1728) was a Puritan minister whose favorite slave was named Onesimus. When Mather observed that Onesimus seemed to be immune to smallpox, he wanted to know why. Onesimus explained his immunity to Mather but was not sure that he would believe the story.

Onesimus told of a procedure used commonly in his homeland in western Africa. A drop of liquid from a smallpox sore was put into a cut on a healthy person's arm. That person would often become slightly ill but would rarely, if ever, get smallpox. The small drop of liquid containing a minute amount of smallpox virus rendered the person who received it permanently immune to the dreaded disease.

Mather told his medical friends about the procedure, a forerunner to vaccination. Most were unwilling to accept the idea and considered it dangerous to purposely infect a person with smallpox. Mather persisted, amid much resistance, until several medical practitioners began to use the procedure described by Onesimus. The results spoke for themselves, as those who were vaccinated became immune to smallpox.

During the 18th century, immunization against smallpox scarcely moved from its Boston birthplace. Not until the 1770s did the English physician Edward Jenner note that milkmaids exposed to cowpox developed nodules on their hands but did not get smallpox. He successfully immunized a boy with pus from a nodule on a milkmaid's hand and then continued to experiment in the face of controversy. He was eventually able to provide vaccine and encourage vaccination throughout Britain.

In 1801 Jenner predicted that vaccination would eradicate smallpox worldwide. In 1980, just 179 years after Jenner's prediction and 274 years after Onesimus told his master how he happened to be immune to smallpox, the World Health Organization made a most dramatic announcement. Because of a successful worldwide vaccination campaign, smallpox was now extinct.