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
For the Term of His Natural Life not stop treating him like an inferior, at one point upsetting Dawes so much that he considers leaving on his own. Only Sylvia's writing in the sand, "Good Mr. Dawes", stops him. Through a hazard, Frere tells Dawes of the fate of his cousin and how narrowly he missed inheriting the Devine fortune. Dawes had not known about Sir Richard's death. Finally, they set to sea with Mrs. Vickers gravely ill and Sylvia soon also sick. After some time they are found by an American vessel at which point Frere takes the rudder of the boat and Sylvia in his