In the 1700s a disease called smallpox killed millions of people every year. It covered the skin in painful blisters and left survivors badly scarred. A country doctor in England named Edward Jenner noticed something odd: milkmaids who caught a much milder cattle illness called cowpox almost never got smallpox.
In 1796 Jenner took fluid from a cowpox blister on a milkmaid’s hand and rubbed it into a small scratch on the arm of an eight-year-old boy named James Phipps. James got a little sick, then got better. When Jenner later exposed him to actual smallpox, the boy stayed perfectly healthy.
That was the world’s first vaccine - and we even named it after this experiment. The Latin word for cow is “vacca.” Two hundred years later, in 1980, the World Health Organization announced smallpox was wiped out everywhere on Earth. It’s the only human disease we have ever completely defeated.
