It was not clear how widely the potential vaccine will be used within China's enormous military establishment.
The experimental shot, developed by a Beijing-based unit of CNBG, has induced high-level antibodies in all the inoculated participants in a Phase 1/2 clinical trial involving 1,120 healthy people, according to preliminary data of the trial, CNBG said in a posting on the social media platform WeChat, without disclosing specific readings.
More than 200 vaccine candidates are at different stages of development and 15 are in human clinical trials, Swaminathan added.
CanSino in a statement filed with Hong Kong Exchanges and Clearing Ltd on Monday said Ad5-nCoV won approval for clinical trials early in March.
"The Ad5-nCoV is now limited to military use only and its use can not be expanded to a broader vaccination range without the approval of the Logistics Support Department", CanSino said, referring to the Central Military Commission department where the military use of the vaccine was approved.
The company did not reveal to Reuters whether the inoculation of the vaccine candidate is mandatory or optional, citing commercial secrets.
As of Monday, the country had tallied 1.35 million cases of COVID-19 and almost 58,000 deaths, according to case tracker Worldometers.
China's military has approved a coronavirus vaccine for use within its ranks. Responding to queries on leading vaccine candidates, Swaminathan said AstraZeneca has the largest global commitment and was the leading candidate in terms of timing.
Other companies, such as Jansen Pharmaceuticals, will start clinical trials based on adenovirus-based vaccines, but said they expect the first results only next year.
But vaccines against viruses are extremely hard to develop, and a "gold standard" preventor - one that lasts six months, is at least 50 per cent effective and can successfully prevent transmission of the virus - will no doubt take time.