China has 21 COVID-19 vaccines entering different stages of clinical trials at present, including 8 currently undergoing third and late stage human trials overseas, a senior health official said on Sunday.

Zeng Yixin, deputy head of the National Health Commission, said one mRNA vaccine developed by Chinese researchers has passed ethics evaluation overseas, a key step before launching clinical trials in foreign countries. The mRNA vaccines, widely considered an innovative strategy, deliver genetic instructions in the form of RNA to trigger the human body to generate an immune response.

Among leading vaccine candidates in China, four have gained conditional market approval for public use, and three candidates have obtained emergency use authorization, he added.

"Since we initiated vaccine development, it took two months to launch clinical trials, four months to issue emergency use approval, five months to launch Phase-3 clinical trials overseas and 11 months to grant conditional market approval," he said.

"China not only has some of the world's highest number of new COVID-19 vaccines, its speed of vaccine development has also broken records," he said.

China is also making headway in creating nasal spray and inhaled COVID-19 vaccines as clinical trials of them are underway, Zeng said, adding experts will study their safety and efficacy after completing the collection of relevant data. Currently, all vaccines approved for use in China and overseas are delivered through injections.

In terms of expanding the use of vaccines to cover people aged 3 to 17, Zeng said experts are discussing the safety and efficacy of them on the younger population. "After relevant governments issue approval, vaccines will be given to the group," Zeng added.