preparation of poliomyelitis virus given to prevent infection with the disease. The virus is grown in kidney tissue from rhesus monkeys (rhesus monkey). There are two types of the vaccine. The first, known as inactivated poliovirus vaccine (IPV) or Salk vaccine (named for its inventor, American physician Jonas Salk (Salk, Jonas Edward)), contains killed virus and is given by injection. The second, known as oral poliovirus vaccine (OPV) or Sabin vaccine (named for its inventor, American physician and microbiologist Albert Sabin (Sabin, Albert Bruce)), contains live attenuated (weakened) virus and is given orally. Vaccines, whether killed or live, may contain strains of all three poliovirus types or of just one. For example, trivalent OPV (tOPV) contains live attenuated virus of all three poliovirus types and thus is effective against all three types of the virus. In contrast, monovalent OPV1 (mOPV1) contains live attenuated virus of only poliovirus type I and thus is effective only against type I virus. In general, for both IPV and OPV, three doses of vaccine are required, with a fourth “booster” given when a child reaches school age. For detailed information on polio treatment and immunization, see polio.