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( Vaccine)
A vaccine is a biological preparation which is used to establish or improve immunity to a particular disease. Vaccines can be prophylactic (e.g. 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). The term "vaccine" derives from Edward Jenner's 1796 use of cowpox (Latin variolæ vaccinæ, adapted from the Latin vaccin-us, from vacca cow), which, when administered to humans, provided them protection against smallpox. The earliest vaccines were based on the concept of variolation originating in China, in which a person is deliberately infected with a weak form of smallpox as a form of inoculation. Jenner realized that milkmaids who had contact with cowpox did not get smallpox. The process of distributing and administrating vaccines is thus referred to as "vaccination". Jenner's work was continued by Louis Pasteur and others in the 19th century. Since vaccination against smallpox was much safer than smallpox inoculation, the latter fell into disuse and was eventually banned in England in 1849.
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