title: Evolution of poliovirus since introduction of attenuated vaccine.
mesh_terms: D004812:Epidemiologic Methods; D006801:Humans; D011051:Poliomyelitis / Q000453:epidemiology*; D017955:Poliovirus / Q000302:isolation & purification; D014613:Vaccines, Attenuated
chemical_list: D014613:Vaccines, Attenuated