Several experimental new coronavirus vaccines are in the final stages of testing.

Several experimental new coronavirus vaccines are in the final stages of testing, officials involved in vaccine development say.

British-Swedish pharmaceutical company AstraZeneca said Monday (Aug. 31) that the final phase of trials in the United States will involve up to 30,000 adults from different racial, ethnic and geographic backgrounds.

A vaccine developed by the National Institutes of Health (NIH) and manufactured by U.S.-based Moderna Inc. also began trials involving thousands of people in the United States this summer. A vaccine developed by New York-based Pfizer Inc. and Germany-based BioNtech Inc. also began such trials.

The company’s AZD1222 vaccine is in the final stages of testing in Brazil, South Africa and the United Kingdom, and additional trials are planned in Japan and Russia, AstraZeneca said.

For experimental vaccines to be successful, they must pass more rigorous testing than other trials because they will be used in healthy people. Experts emphasize that final-stage trials must be conducted in large populations to determine whether the vaccines are safe and effective enough for widespread vaccination.