The British scientist Edward Jenner (1749–1823), as a boy in the mid-1700s, reportedly overheard a dairymaid mention that because she’d lived through a case of cowpox, she was safe from the smallpox epidemic ravaging Europe. Today, we have that chance encounter to thank for the eradication of the deadly smallpox virus.

Smallpox probably originated in Africa, spreading to India and then to Europe around AD 700. By the 18th century in Europe, 400,000 people died of smallpox annually, and many survivors went blind or were left with disfiguring scars. The disease was called variola—or small pox, to distinguish the illness from syphilis, which was called “the Great Pox.”

Because those who did survive smallpox became immune to later exposure, a procedure called variolation—known today as inoculation—became popular: A sample of body fluid taken from a pustule of someone who was sick with smallpox was injected under the skin of an uninfected person. Although a small percentage of patients developed full-blown smallpox (or another blood-transmitted disease), most came down with only a milder case and survived.

Variolated as a young boy, Edward Jenner grew up to become a renowned biologist in England. He had always been curious about how cowpox could protect against smallpox, and in 1796, he injected pus from the arm of a dairymaid sick with cowpox into an 8-year-old boy. The boy came down with a fever and mild cold, but when Jenner later injected him with smallpox, the boy developed no infection. Jenner called the procedure vaccination, a word he coined from the Latin vaca, for “cow.”

The practice of vaccination spread to most European countries and reached America by 1800, while variolation was phased out. The mid-1900s saw the development of more stable, freeze-dried vaccines, and smallpox was declared extinct worldwide in 1980. Vaccinations work by tricking the immune system into producing immune cells that protect against the real disease-causing organism. Since Jenner’s discovery, vaccines for influenza, pneumonia, rabies, meningitis, and other serious conditions have been developed.

ADDITIONAL FACTS

  1. It’s now recognized that Benjamin Jesty (1737–1816) was probably the first person to use cowpox to vaccinate against smallpox, performing the procedure on himself and his family in 1774. Jenner gets credit, however, for popularizing the technique throughout the world.
  2. Jenner was also interested in hot-air balloons, and he built and launched a successful model in 1784.
  3. Smallpox has been identified as a possible agent of bioterrorism, especially since the September 11, 2001, terrorist attacks. Some doctors have gone so far as to suggest preemptive vaccinations.