EDWARD JENNER VACCINATING HIS FAMILY WITH COWPOX WHILE A COW LOOKS ON IN THE BACKGROUND

For seven decades after the Boston experiments, inoculation remained humanity’s best medicine against smallpox. It was also extremely hazardous. Finally, in 1798, a doctor named Edward Jenner announced a safer new way to fight the dreaded disease. He found his solution on farms in the English countryside.

Jenner was puzzled when he noticed that smallpox inoculation didn’t always work on farmers and milkmaids. When he scratched their arms and introduced smallpox germs, they didn’t get sick. In fact, nothing happened at all. They appeared to already be immune to smallpox, even though they’d never had smallpox before. How was that possible?

Jenner learned that farm workers were sometimes infected with an illness they caught from their cows. “Cow- pox” made people sick and produced a small number of blisters, but it wasn’t deadly. Jenner wondered if recovering from cowpox made people immune to smallpox? To find out, Jenner tried smallpox inoculation on several people who previously had cases of cowpox. None of them became infected with smallpox.