Several experimental COVID-19 vaccines have reached the final testing stage, officials involved in their development have said.The British-Swedish pharmaceutical company, AstraZeneca, said Monday the final testing stage in the U.S. will involve up to 30,000 adults from different racial, ethnic and geographical groups.
A vaccine created by the U.S. National Institutes of Health and manufactured by the U.S.-based Moderna Inc. also began testing thousands of people this summer in the U.S., as has another experimental vaccine developed jointly by Pfizer Inc., headquartered in New York, and Germany’s BioNtech.
AstraZeneca said its vaccine, known as AZD1222, is in late-stage trials in Brazil, South Africa and Britian, and that other trials of the vaccine are planned in Japan and Russia.For the experimental vaccines to be successful, they must pass tests that are more stringent than those in other trials because they will be administered to healthy people. Experts emphasize that final testing must be conducted among large numbers of people to determine whether the vaccines are safe and effective enough for mass vaccinations. 
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