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preparation of poliomyelitis virus given to prevent infection with the disease. The virus is grown in kidney tissue from rhesus monkeys. There are two types of vaccine: one with killed virus, which is injected, and the other with live, attenuated (weakened) virus, which is given orally. Vaccines, whether killed or live, must contain strains of all of the three poliovirus types, and three doses are required, as the body develops immunity to only one type at a time.