Original: The term vaccine derives from Edward Jenner 's 1796 use of the term cow pox ( Latin variolÃ vaccinÃ , adapted from the Latin vaccÄ '' n-us , from vacca cow ) , which , when administered to humans , provided them protection against smallpox .
Simplified: The term derives from the Latin vaccÄ '' n-us ( from vacca cow ) ; in 1796 Edward Jenner used cows infected with cowpox ( variolae vaccinae ) to protect people against smallpox .