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.
The flags of Qatar and Bahrain are very similar, reflecting the countries' historical links. The proportions of the Qatari flag are unique. Effective date: c. 1949.