Researchers are conducting phase-1 and phase-2 clinical trials on a China-made inhaled COVID-19 vaccine, a Chinese health official said Friday.

After completing the collection of clinical-trial data, experts will study the safety and effectiveness of the inhaled vaccine, a modified version of an injectable adenovirus vector COVID-19 vaccine that has already hit the market, said Shao Yiming, a researcher at the Chinese Center for Disease Control and Prevention, at a press conference.

The inhaled COVID-19 vaccine was jointly-developed by researchers from the Institute of Military Medicine under the Academy of Military Sciences and China's CanSino Biologics Inc.

Inhaled or nasal-spray vaccines were selected as one of China's vaccine technologies to combat COVID-19 from the very beginning, Shao added.

Another nasal-spray COVID-19 vaccine, developed by Xiamen University, the University of Hong Kong and Beijing Wantai Biological Pharmacy, has completed phase-1 and phase-2 trials. Researchers are applying phase-3 clinical trials overseas, to further evaluate the efficacy of the vaccine, according to Shao.

Over 845.2 million doses of COVID-19 vaccines had been administered across China as of Thursday, the National Health Commission said Friday.