Polio vaccine incidents reduced public confidence in polio vaccine leading to a drop in vaccination rates. At the same time that Salk was testing his vaccine, both Albert Sabin and Hilary Koprowski continued working on developing a vaccine using live virus. During a meeting in Stockholm to discuss polio vaccines in November 1955, Sabin presented results obtained on a group of 80 volunteers, while Koprowski read a paper detailing the findings of a trial enrolling 150 people. Sabin and Koprowski both eventually succeeded in developing vaccines. Because of the commitment to the Salk vaccine in America, Sabin and Koprowski both did their
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