Here's a little more detail about the vaccine from another source:
Sabin and the Cold War
Because Salk vaccine was used so extensively in the United States, Sabin had to go overseas in the late 1950s to find people for his clinical trials, in the Belgian Congo and, on a massive scale, in the Soviet Union. An American was able to conduct an extensive polio vaccine trial in the Soviet Union at the height of the cold war because the fear of polio was stronger than political differences.
After getting satisfactory results of tests of your vaccine in 20,000 children we are going to prepare from your strains (1956) material for vaccination of 2ñ3 million people more, and after thorough laboratory tests of this vaccine, to use it in our country in 1959.
Dr. Mikhail Chumakov to Albert Sabin, letter of December 26, 1958
In the first five months of 1959, ten million children in the Soviet Union received the Sabin oral vaccine. Albert Sabin received a medal in gratitude from the Russian government during the height of the cold war.
http://americanhistory.si.edu/polio/virusvaccine/vacraces2.htm
Sabin and the Cold War
Because Salk vaccine was used so extensively in the United States, Sabin had to go overseas in the late 1950s to find people for his clinical trials, in the Belgian Congo and, on a massive scale, in the Soviet Union. An American was able to conduct an extensive polio vaccine trial in the Soviet Union at the height of the cold war because the fear of polio was stronger than political differences.
After getting satisfactory results of tests of your vaccine in 20,000 children we are going to prepare from your strains (1956) material for vaccination of 2ñ3 million people more, and after thorough laboratory tests of this vaccine, to use it in our country in 1959.
Dr. Mikhail Chumakov to Albert Sabin, letter of December 26, 1958
In the first five months of 1959, ten million children in the Soviet Union received the Sabin oral vaccine. Albert Sabin received a medal in gratitude from the Russian government during the height of the cold war.
http://americanhistory.si.edu/polio/virusvaccine/vacraces2.htm