CanSino Biologics Inc. will start testing its coronavirus vaccine candidate in late-stage human trials in Argentina and Chile, the co-founder of the Chinese pharmaceutical company said on Saturday.

The candidate Ad5-nCoV uses a harmless common cold virus to carry genetic information of coronavirus' protein to elicit immune responses has already begun Phase III trials in Pakistan, Russia and Mexico.

CanSino will begin interim analysis of the late-stage trial results when 50 infection cases are found, said Zhu Tao, who is also the company's chief scientific officer.

The 50-case milestone could be hit faster than previously expected judging from how the virus is spreading, Zhu told an industry event, without specifying when the analysis would start.

The expectation follows announcements this month by Pfizer Inc and BioNTech and Moderna, as well as from Russia, that their experimental vaccines are more than 90 percent effective, according to interim data from large trials.

China has five home-grown candidates currently undergoing Phase III trials. None have so far produced interim results.

CanSino said in June that their candidate vaccine, which is being co-developed with a research institute affiliated to China's military, had been approved for use in military personnel.

Many military personnel, including peacekeepers in places where COVID-19 remains, have taken the vaccine, and none have been infected, CanSino chief executive Yu Xuefeng told a healthcare forum on Friday.

Yu said he "has great confidence" in the product but cautioned that the final conclusion requires scientific data.

CanSino agreed in October to supply 35 million doses of the vaccine to Mexico.