The World Health Organization (WHO) supported China's decision to vaccinate high-risk people against coronavirus in July this year while clinical trials were still under way, a Chinese health official said on Friday.

China launched its emergency program in July, having communicated with the WHO in late June, according to Zheng Zhongwei, a National Health Commission official.

Read more: China approves emergency usage of COVID-19 vaccines, official says

Hundreds of thousands of essential medical workers and other limited groups of people considered at high risk of infection have been given the vaccine. "We've made it very clear that the COVID-19 vaccine we put into emergency use are safe," Zheng said. "Their safety can be ensured but their efficacy is yet to be determined."

"After the approval, on June 29, China's State Council made a communication with the relevant representatives of the WHO Office in China, and obtained support and understanding from the WHO," Zheng told a news conference.

Countries have autonomy to issue emergency use authorization for any health product according to the national regulations and legislations, Dr. Mariangela Simão, assistant director-general at the WHO, said at a news conference in Geneva on Friday.

WHO chief scientist Soumya Swaminathan said earlier this month that emergency use authorization for coronavirus vaccine is a "temporary solution," and that the long-term solution lay in completion of Phase 3 trials.

At least three vaccine candidates, including two developed by state-backed China National Biotec Group (CNBG) and one from Sinovac Biotech now in Phase 3 trials overseas, are included in the emergency use program.

A fourth experimental vaccine developed by CanSino Biologics was approved to be used in the Chinese military in June.

(With input from Reuters)