BEIJING — The second phase of clinical trials for COVID-19 vaccines is expected to be completed successively beginning in July, and no major adverse reactions from the trials had been reported so far, a Chinese official said on May 15.

The vaccines undergoing clinical trials include one adenovirus vector vaccine and four inactivated vaccines fast-tracked by China's National Medical Products Administration, Zeng Yixin, a senior official with the National Health Commission, said at a news conference.

A total of 2,036 volunteer participants have been inoculated for the second phase of clinical trials and researchers are assessing whether or not the vaccines are safe and effective, according to Zeng.