The production of immunity to a disease by inoculation
of an attenuated form of the virus causing the disease.
N amed after the English physician Edward Jenner (1749-1823). Jenner exploited
the folk knowledge that people who caught cowpox from their cows could not catch
smallpox to develop a method of vaccination against smallpox using an attenuated
form of the virus. Also known as Jenner's method and the jennerian method.
The story, briefly told, is as follows. In May 1796 a dairymaid, Sarah Nelmes,
consulted Dr. Jenner about a rash on her hand. He diagnosed cowpox and Sarah confirmed
that one of her cows, a Glouchester cow named Blossom, had recently had cowpox,
a mild infection of cows that causes a some weeping spots called pocks on their
udders, but nothing more. Milkmaids occasionally caught cowpox from the cows. Although
they developed a small number of pocks, usually on the hand, and they might become
mildly ill, the disease did not otherwise trouble them. It was also known that cowpox
could pass not only from cow to person from person to person.
Jenner decided to test the protective properties of cowpox by giving it to someone
who had not yet had smallpox. He selected James Phipps, the 8-year-old son of his
gardener and on May 14 made a few scratches on James' arm and rubbed into them some
material from one of the pocks on Sarah's hand. A few days later James became mildly
ill with cowpox but was well again a week later. To test whether the cowpox would
protect James from smallpox, on July 1 Jenner variolated him by scratching into
his skin scab material from someone with smallpox. James did not develop smallpox
then or later.
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