Polio vaccine attenuated vaccine strains. In 1958, the National Institutes of Health created a special committee on live polio vaccines. The various vaccines were carefully evaluated for their ability to induce immunity to polio, while retaining a low incidence of neuropathogenicity in monkeys. Large-scale clinical trials performed in the Soviet Union in late 1950s to early 1960s by Mikhail Chumakov and his colleagues demonstrated safety and high efficacy of the vaccine. Based on these results, the Sabin strains were chosen for worldwide distribution. Fifty-seven nucleotide substitutions distinguish the attenuated Sabin 1 strain from its virulent parent (the Mahoney serotype), two nucleotide substitutions
How the Riddler Got His Name Amanda Bell of "EW" gave the episode a "B+" and wrote, "The content of Nygma's riddles was paralleled not just by his own experience coming into his big badness, but also in the episode's other two story lines. 514A is, obviously, a literal reflection of Bruce Wayne, and the loneliness referred to in the first riddle applies to both Nygma and Gordon. Gordon's quest for truth and family, compounded by his current isolation, makes him vulnerable to Frank’s ploy right now — if that's what it actually is. For a segment devoted to such a cunning wordsmith, this episode quite