An experimental Covid-19 vaccine developed by Sanofi and GlaxoSmithKline showed a robust immune response in early-stage clinical trial results, enabling them to move to a late-stage study, said the French drugmaker.

Sanofi and Britain's GSK said a global Phase III trial would start in the coming weeks and involve more than 35,000 adults, with the hope of seeing the vaccine approved by the fourth quarter after having initially targeted the first half of this year before a setback.

"The Phase 2 interim results showed 95 per cent to 100pc seroconversion following a second injection in all age groups (18 to 95 years old) and across all doses, with acceptable tolerability and no safety concerns," Sanofi said.