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==Mechanism==
If the body produces an antibody against a particular disease or toxin , it can identify the infection early on and the [[immune system]] can destroy it. Vaccines work by exposing the body to a form of the disease in such a way that it is much less likely to cause illness but still allows antibodies to develop. This confers a level of immunity to the person or animal vaccinated.<ref>http://www.howstuffworks.com/immune-system7.htm How stuff works: Antibodies</ref>
Since the adoption of mass vaccination programs, many diseases have been curbed. [[Smallpox]], a contagious disease that killed 30 percent of those it infected, has been entirely eliminated through vaccination, excepting some strains maintained in labs for research purposes. Vaccination programs of the 19th and 20th century were effective at curbing the disease, and in 1979 the World Health Organization declared smallpox to be eradicated.<ref>https://www.cdc.gov/smallpox/history/history.html</ref>
