Smallpox Vaccine Invented

In 1796, the English country doctor Edward Jenner carried out an experiment that launched the science of vaccination. By deliberately inoculating a boy with material from a cowpox sore, he showed that a mild disease could protect against smallpox, one of the deadliest illnesses in human history. The method he described eventually grew into a global campaign that, in 1980, led the World Health Organization to declare smallpox eradicated, the only human disease so far to be wiped out.

Smallpox had killed and disfigured people for centuries, and in eighteenth-century Europe it was a leading cause of death, especially among children. Survivors were often scarred or blinded, but they were also immune for life. That observation underlay variolation, a practice known in Asia and Africa and popularized in Britain in the 1720s, partly through Lady Mary Wortley Montagu. It involved giving a person material from a smallpox sore to cause a milder, controlled infection. It worked, but it could still kill and could spread the disease to others.

Jenner, who practiced in Gloucestershire, was aware of a piece of rural folk knowledge: milkmaids who had caught cowpox from cattle seemed not to catch smallpox. He was not the only person to have noticed this, and some others had already tried deliberate cowpox inoculation. In May 1796, he took matter from a cowpox lesion on a dairymaid, Sarah Nelmes, and inoculated an eight-year-old boy, James Phipps. Weeks later he exposed the boy to smallpox material, and Phipps did not develop the disease. Modern ethical standards would condemn the experiment, but it was not unusual for its time.

Jenner repeated his tests on more subjects and published his findings in 1798. The Royal Society had earlier been unreceptive to his initial report, but his pamphlet attracted wide attention. The word "vaccine" comes from the Latin vacca, meaning cow. Vaccination spread quickly across Europe, to the Americas, and to Asia, often backed by governments, and it proved safer than variolation. Some doctors and members of the public resisted it, a pattern of controversy that would recur with later vaccines.

The long-term consequences were immense. Jenner's work laid the groundwork for immunology, though the underlying mechanisms of immunity were not understood until much later, and Louis Pasteur extended the principle to other diseases in the nineteenth century. Vaccination against smallpox became compulsory in several countries. In 1967 the WHO launched an intensified eradication program built on surveillance and targeted vaccination, and the last natural case occurred in Somalia in 1977. Jenner's experiment of 1796 stands as a landmark in preventive medicine.