Chinese vaccine developer CanSino Biologics is in talks with Russia, Brazil, Chile and Saudi Arabia to launch a Phase III trial of its experimental COVID-19 vaccine, its co-founder said on Saturday.

China's success in driving down COVID-19 infections has made it harder to conduct large-scale vaccine trials, and so far only a few countries have agreed to work with it.

"We are contacting Russia, Brazil, Chile and Saudi Arabia (for the Phase III trial), and it's still in discussion," Qiu Dongxu, executive director and co-founder of CanSino, told an anti-viral drug development conference in Suzhou, eastern China.