Russian-born US microbiologist who developed a highly effective, live vaccine against polio. The earlier vaccine, developed by physicist Jonas Salk, was based on heat-killed viruses. Sabin was convinced that a live form would be longer-lasting and more effective, and in 1957 he succeeded in weakening the virus so that it lost its virulence. The vaccine can be given by mouth.
Yellow represents the golden land of South America. Blue stands for the ocean separating the country from Spain. Red symbolizes the blood and courage of the people resisting the tyrants. Effective date: 26 November 1861.