The move has prompted concerns among onlookers that China is pushing ahead to gain an edge in the race to develop a successful vaccine without following proper safety measures.
Chinese companies Sinopharm and SinoVac have given vaccine shots to more than 350,000 people in recent months and that number is likely set to rise.
The inoculations have been performed under an emergency use designation that was approved in June.
SinoVac has also provided tens of thousands of rounds of its CoronaVac for the Beijing city government.
Another candidate being jointly developed by the military and CanSino, a biopharmaceutical company, has been approved for emergency use in military personnel.
Now large Chinese firms including telecom giant Huawei and broadcaster Phoenix TV has announced they are working with Sinopharm to get the vaccine for their employees.
A health official said that China, which claims to have largely controlled the disease, needs to take steps to prevent it from coming back.
Zheng Zhongwei said at a news conference that the Chinese government referenced the World Health Organisation’s emergency-use principles to create its own through a strict process.
Mr Zheng said there have been no serious side effects in the clinical trials.
Kan Chai, a popular writer who was among those injected with the vaccine, said he had no reaction after the first dose.
But he began to feel sleepy after the second shot, saying: “When I was driving on the road, I suddenly felt a bit dizzy, as if I was driving drunk.
“So I specially found a place to stop the car, rest a bit and then I felt better.”
Mr Zheng said that under the emergency rule, high-risk personnel such as medical and customs workers and those who have to work overseas are given priority access, he said. He declined to provide exact numbers.
“In China’s case, the pressure in preventing imported infections and domestic resurgence is still huge,” Zheng added.
In an established but limited practice, experimental medications have been approved historically for use when they are still in the third and last phase of human trials. Chinese companies have four vaccines in phase three – two from Sinopharm and one each from Sinovac and CanSino.
However, Diego Silva, a lecturer in Bioethics at the University of Sydney, said that giving vaccines to hundreds of thousands outside of clinical trials does not have “scientific merit” in China, where there are currently very few locally transmitted cases, and incoming arrivals are quarantined centrally.
“If it’s in the US where the virus is still raging that’s a bit different, but in a country like China it doesn’t seem to make sense to me,” he said.
“Because there’s not enough of the virus in China locally to deduce anything, you’re introducing a whole host of others factors”, by injecting people outside of trials.
There are 11 coronavirus vaccines in late-stage clinical trials. Two are in the UK: a potential vaccine being developed by Oxford University and British biopharmaceutical firm AstraZeneca, alongside an effort by US pharmaceutical firm Novavax.