Roundup: U.S. steps up COVID-19 vaccine development as another vaccine candidate starts final phase trial

WASHINGTON, Sept. 1 (Xinhua) -- Researchers across the United States are stepping up efforts to work out an effective COVID-19 vaccine as another vaccine candidate has started phase 3 clinical trial on Monday.

The multi-site clinical trial evaluating an investigational COVID-19 vaccine, known as AZD1222, will enroll approximately 30,000 adult volunteers at 80 sites in the United States to evaluate if the candidate vaccine can prevent COVID-19, said the U.S. National Institutes of Health (NIH).