Jenner, Edward (1749–1823)

Edward Jenner is best known as the inventor of the smallpox vaccination. Although little of the basic science of the smallpox virus or human immunity was known at the time, Jenner tested a hypothesis formulated by epidemiologic observation in a clinical trial (with an n of 1) and established its validity. His research provided the model for the next 150 years of human medical research.

Jenner was born, and spent most of his career as a country doctor, in the English county of Gloucestershire. Orphaned at age 5, he was sent to boarding school at age 8, where he was inoculated with smallpox and reportedly traumatized by the experience. At the age of 12, he began surgical training.

Jenner observed that most milkmaids and cowmen did not get smallpox, a widespread disease that killed many infants and small children and often left the few who did survive deaf, blind, and horribly scarred. Jenner established that these immunized individuals had all suffered from cowpox, a relatively mild disorder characterized by skin blisters, and hypothesized that having had cowpox somehow prevented one from acquiring smallpox. In 1796, Jenner inoculated cowpox lymph derived from a cowpox vesicle on the skin of dairymaid Sarah Nelmes into a young boy named James Phipps. Phipps's cowpox took a normal course, and he recovered. A month later, Jenner inoculated the boy with the smallpox virus and no reaction occurred. After repeating the inoculation a few months later, smallpox still did not develop.

Jenner was not the first to suggest that cowpox infection provided immunity to smallpox or the first to attempt cowpox inoculation to prevent smallpox. He was however the first scientist to demonstrate by experiment that naturally acquired cowpox protected against smallpox. Jenner coined the word vaccination for his treatment (vacca means cow in Latin). Louis Pasteur eventually adopted this term for immunization against any disease.

Jenner eventually gave up his life as a country doctor and spent considerable time and money promoting vaccination. His 1798 book An Inquiry Into the Causes and Effects of the Variolae Vaccinae received favorable as well as critical reviews. Controversy dominated the rest of Jenner's life. Although he was often ridiculed for his work on immunization, scientific advances in the areas of germ theory, viruses, and human immunity support Jenner's main conclusions. Ultimately, Jenner's vaccination enabled the eradication of smallpox. In 1980, the World Health Assembly declared the world free from endemic smallpox as a direct result of Jenner's discovery.