Edward Jenner

By Lin Yue

The Gloucestershire milkmaids knew it before the doctors did: no one who had caught cowpox — the mild blisters milkers got on their hands — ever caught smallpox. Edward Jenner, born in Berkeley in 1749, the son of a clergyman, heard it as a young apprentice surgeon and never forgot it. After training in London under the great surgeon John Hunter — whose advice, don't think, try, became his motto — he returned to country practice, and spent twenty years testing the milkmaids' lore against observation, tracking who got cowpox and who escaped smallpox.

In 1796 he did the experiment that changed the world. He took matter from a cowpox blister on the hand of the milkmaid Sarah Nelmes and scratched it into the arm of eight-year-old James Phipps, the gardener's son. The boy developed cowpox, recovered — and then Jenner did the part that would be unthinkable today: he deliberately exposed the child to smallpox, by variolation. Nothing happened. The boy was immune. Jenner repeated the trial on others, including his own infant son, and in 1798 published the Inquiry into the Causes and Effects of the Variolae Vaccinae — seventy-five pages that founded immunology. Vaccination — from vacca, the cow — was born.

The reception was ferocious and then triumphant. Cartoonists drew cows sprouting from vaccinated arms; the clergy denounced interference with Providence; rival doctors claimed priority. But the numbers were undeniable, and royalty led the way: the Prince of Wales had his children vaccinated. Within a decade vaccination circled the globe — Thomas Jefferson had his family and slaves vaccinated, Napoleon had his army done, the Spanish crown mounted the Balmis expedition to carry the vaccine to the Americas and the Philippines. Parliament voted Jenner £30,000, a fortune; he spent it on his village practice and his garden.

Smallpox killed some 300 million people in the twentieth century alone — more than all its wars — before the World Health Organization eradicated it in 1980, using Jenner's principle. He died in 1823 of a stroke, in the same Berkeley house where he was born. The milkmaids were right, and the country doctor who believed them saved more lives than any physician in history.

Impact on civilization

Jenner's vaccination founded immunology and proved that a mild infection could confer protection against a deadly one — the principle behind every vaccine ever made. Smallpox vaccination spread worldwide within a decade, the first global public-health campaign, and its descendant eradicated smallpox entirely in 1980: the only human disease ever wiped out, and the single greatest life-saving achievement in medical history. Jenner established the ethics and method of the clinical trial — test, challenge, publish — and showed that folk observation, rigorously tested, could outrank medical doctrine. Every syringe in every clinic descends from Sarah Nelmes's blister.