French vaccin, from vaccine cowpox, from New Latin vaccina (in variolae vaccinae cowpox), from Latin, feminine of vaccinus, adjective, of or from cows, from vacca cow; akin to Sanskrit vaśa cow
The term vaccine derives from Edward Jenner's 1796 use of cow pox to inoculate humans, providing them protection against smallpox.
1: a preparation of killed microorganisms, living attenuated organisms, or living fully virulent organisms that is administered to produce or artificially increase immunity to a particular disease
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.
Vaccines can be prophylactic (example: to prevent or ameliorate the effects of a future infection by any natural or "wild" pathogen), or therapeutic (e.g. vaccines against cancer are also being investigated; see cancer vaccine.