Cowpox
Like any other doctor of the time, Edward Jenner carried out variolation to protect his patients from smallpox. However, from the early days of his career Edward Jenner had been intrigued by country-lore which said that people who caught cowpox from their cows could not catch smallpox. This and his own experience of variolation as a boy and the risks that accompanied it led him to undertake the most important research of his life.
Cowpox is a mild viral infection of cows. It causes a few weeping spots (pocks) on their udders, but little discomfort. Milkmaids occasionally caught cowpox from the cows. Although they felt rather off-colour for a few days and developed a small number of pocks, usually on the hand, the disease did not trouble them.
The First Vaccination
In May 1796 a dairymaid, Sarah Nelmes, consulted Jenner about a rash on her hand. He diagnosed cowpox rather than smallpox and Sarah confirmed that one of her cows, a Gloucester cow called Blossom, had recently had cowpox. Edward Jenner realised that this was his opportunity to test the protective properties of cowpox by giving it to someone who had not yet suffered smallpox.
He chose James Phipps, the eight-year old son of his gardener. On 14th May he made a few scratches on one of James' arms 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. So Jenner knew that cowpox could pass from person to person as well as from cow to person.
The next step was to test whether the cowpox would now protect James from smallpox. On 1st July Jenner variolated the boy. As Jenner anticipated, and undoubtedly to his great relief, James did not develop smallpox, either on this occasion or on the many subsequent ones when his immunity was tested again.
Publication
Jenner followed up this experiment with many others. In 1798 he published all his research into smallpox in a book entitled 'An Inquiry into the Causes and Effects of the Variolae Vaccinae; a Disease Discovered in some of the Western Counties of England, Particularly Gloucestershire, and Known by the Name of The Cow Pox'.
In each of the next two years he published the results of further experiments, which confirmed his original theory that cowpox did indeed protect against smallpox.
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