Smallpox
The first vaccine for smallpox used the results of cowpox infections. It was invented by Edward Jenner. It was used to stop people from getting smallpox.  The word "vaccine" came from "vaccina", the Latin word for cow, because cowpox was used. The WHO (World Health Organisation) vaccinated people all over the world. In 1980, the WHO said the disease no longer existed, and no one would ever get sick from it again. Live copies of smallpox are kept in maximum-security laboratories around the world to make sure the disease can never infect people again.