The Covid-19 vaccine developed by China's Sinovac Biotech has an efficacy of 83.5 percent based on final results of Phase III trials, Turkish researchers said on Wednesday, a downward revision from a preliminary finding of 91.25 percent.

The final efficacy rate was based on 41 infections, 32 of which had received a placebo, said Murat Akova, head of the Phase III trials conducted in Turkey...