Vaccination
In 1796 an English doctor, Edward Jenner, noticed something. He saw that people who got cowpox did not get sick from smallpox. He gave a young boy the cowpox virus to protect him from smallpox. This was done by scratching liquid from cowpox sores into the boy's skin. This same method using the liquid from sores was also used to give people smallpox. People did this so they might get smallpox on one place on their bodies. Then they could pick which body part got scars from smallpox. But sometimes people who did this got very sick from smallpox. Some even died. This was a dangerous thing to do. But people did it because it was less dangerous than getting smallpox.