How it began
Edward Jenner, a physician born in Berkeley, Gloucestershire, had long heard that dairymaids who caught cowpox were protected from smallpox. On 14 May 1796 he took matter from cowpox lesions on the hand of a dairymaid, Sarah Nelms, and inoculated an eight-year-old boy, James Phipps. In July 1796 he inoculated the boy with matter from a fresh smallpox lesion, and no disease developed. In 1798 he privately published his Inquiry describing the work, and he named the procedure vaccination after the Latin word for cow.
Before it existed
Before 1796 the only known way to prevent smallpox was variolation, the deliberate infection of a person with material from someone who had smallpox. The aim was to cause an immune response without a full-blown infection. That did not always succeed, but the risk of death from variolation was lower than from catching smallpox naturally.
How it spread
Vaccination became popular in London through others, including the surgeon Henry Cline, to whom Jenner had given some inoculant. Jenner sent vaccine to anyone who asked, and recipients passed it on. By 1800 the practice had reached most European countries. Benjamin Waterhouse of Harvard introduced it in New England and persuaded Thomas Jefferson to try it in Virginia. By 1803 Jenner's findings had been translated into French and Spanish, and the King of Spain launched a vaccination campaign to the Americas and the Far East.
Who pushed back
In 1797 the Royal Society rejected Jenner's short paper on his experiment. The published Inquiry met a mixed reaction in the medical community, and when Jenner went to London to find volunteers he found none in three months. He was honored and attacked in roughly equal measure, and opponents of vaccination used supposed defects in his earlier study of the cuckoo to cast doubt on his other work.
What lasted
Vaccination gradually replaced variolation, which was prohibited in England in 1840. Parliament granted Jenner 10,000 pounds in 1802 and a further 20,000 pounds five years later. Later science, including germ theory and immunology, supported his main conclusions. The promotion of vaccination enabled the global eradication of smallpox in the late 20th century.
