Edward Jenner

Edward Jenner expiereimented with the pus of cowpox sores to make a vaccination for smallpox because he noticed the people that workedwith cows weren't getting smallpox. He injected a child with the cowpox. The child recovered from the cowpox. Afterwards he injected the child with smallpox and the kid didn't get it because of the built up immunity from the cowpox.