Jonas Salk when the Salk vaccine was introduced, polio was considered one of the most frightening public health problems in the world. In the postwar United States, annual epidemics were increasingly devastating. The 1952 U.S. epidemic was the worst outbreak in the nation's history. Of nearly 58,000 cases reported that year, 3,145 people died and 21,269 were left with mild to disabling paralysis, with most of its victims being children. The "public reaction was to a plague", said historian William L. O'Neill. "Citizens of urban areas were to be terrified every summer when this frightful visitor returned." According to a 2009 PBS
Cold War tensions and the polio vaccine flew to Leningrad in June, 1956. As a result of a cooperation of Sabin and Chumakov in Leningrad, Sabin was able to test his attenuated vaccine when funding in America was declined. While Sabin was working behind the Iron Curtain, the Sabin-Chumakov vaccine was determined to be safe and effective. Cold War tensions caused Western scientists to refuse the reports from the Russians about the effectiveness of the Sabin vaccine. However, mass vaccinations of Sabin's vaccine spread throughout Eastern Europe from 1960–1963. Just as some Soviet virologists did not trust the Western Salk vaccine, Americans had similar reservations about the