BEIJING -- China's COVID-19 vaccine development has entered the "final sprint," with the country preparing for the mass production of COVID-19 vaccines, according to an official from the National Health Commission (NHC).

The evaluation of a vaccine requires a number of comprehensive indicators, of which safety, effectiveness, accessibility and affordability are the most important, said Zheng Zhongwei, an official from the NHC.

China has adopted five technological approaches in developing COVID-19 vaccines, with 15 vaccines entering clinical trials, of which five are undergoing phase-3 clinical trials.

China is scientifically and rigorously promoting phase-3 clinical trials of COVID-19 vaccines and conducting review and approval in strict accordance with laws, regulations and internationally recognized technical standards to ensure the vaccines are safe, effective and can stand the test of time, according to Zheng.

The five vaccines in phase-3 clinical trials include two inactivated vaccines developed by the China National Biotec Group affiliated to Sinopharm, an inactivated vaccine developed by Sinovac Biotech, an adenovirus vector vaccine developed by the Academy of Military Sciences and CanSino Biologics Inc., and a recombinant sub-unit vaccine jointly developed by Anhui Zhifei Longcom Biopharmaceutical Co., Ltd. and the Institute of Microbiology under the Chinese Academy of Sciences.

As the epidemic has been effectively controlled in China, the country no longer has the conditions to carry out phase-3 clinical trials. These are being carried out overseas, which also brings some difficulties and challenges, according to Zheng.

China granted emergency use of COVID-19 vaccines in June.