Edward Jenner and the dairymaid

Small pox has plagued mankind since time immemorial, causing huge epidemics with great loss of life and often changing the course of history. The disease could be prevented or ameliorated by variolation, the subcutaneous inoculation with fluid from smallpox lesions into non-immune individuals. Variolation had been used for centuries, even for members of royal families. It usually caused a milder disease than smallpox but had a 2-3 percent mortality.1

The landscape of smallpox prevention changed dramatically in 1796 when an English physician, Edward Jenner, learned that persons would be immune to smallpox if they had had cowpox – a condition manifested by pustules on the udders of cows and sometimes causing a mild disease in humans. Cowpox is caused by the vaccinia virus (vacca =cow), a member of the pox family of orthopox viruses, immunologically related to the variola virus of smallpox.

Hearing that persons exposed to cowpox were immune to smallpox, Jenner embarked on an experiment that today might have problems with an institutional review committee. In May 1796, he used material from the cowpox lesions of young dairymaid Sarah Nelms to inoculate the eight year old James Phipps. The boy had a mild fever for one day but no other symptoms. When two months later Jenner inoculated the boy with material from a fresh smallpox lesion, the boy did not develop the disease. At first the medical profession was skeptical of Jenner’s finding, but eventually they were convinced. Within a few years doctors began to use vaccination; variolation was abandoned and become illegal (in England in 1840).

But from where did Jenner learn about cowpox? It had long been assumed it was from a milkmaid. Now it turns out that the milkmaid story is apocryphal, invented by Jenner’s biographer several years after his death. It was John Fewster, a Gloucestershire surgeon, who made the first observation, noting that farmers who had had cowpox were immune to smallpox and could not be variolated against it. Fewster paid little attention to this fact but mentioned it at a meeting of the local medical society of which Jenner was a member. So it was from Fewster’s observation that Jenner heard about the cow pox. It does not detract from Jenner’s merit but debunks the “myth of the milkmaid.”



  1. Boylston, A.,W: The myth of the milkmaid. New England Journal of Medicine, 2018,378:414 (1 February)


Additional Reading in Hektoen International

Nils Rosén von Rosenstein: founder of pediatrics, by Einar Perman
Matushka’s ordeal, by Sarah Jane Irawa
Edward Jenner (1749-1823): from variolation to vaccination, by Damiano Rondelli
Smallpox vaccination in the satirical work of James Gillray, by Godfrey Pearlson
Bugs and people: when epidemics change history, by Salvatore Mangione
Smallpox inoculation: prelude to vaccination, by Art Boylston
Washington’s deadliest enemy, by Kathryn Tone



GEORGE DUNEA, MD, Editor-in-Chief (Spring 2018)


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