Expanded programme on immunization.
D002675:Child, Preschool; D003906:Developing Countries; D006801:Humans; D010175:Pan American Health Organization; D011051:Poliomyelitis / Q000517:prevention & control* / Q000635:transmission; D011055:Poliovirus Vaccine, Oral / Q000008:administration & dosage*; D011159:Population Surveillance
D011055:Poliovirus Vaccine, Oral