Russia's Sputnik V vaccine is 91.6 percent effective against symptomatic Covid-19, according to an analysis published in The Lancet on Tuesday that independent experts said allayed transparency concerns over the jab, which Moscow is already rolling out.

The preliminary findings show that the two-dose Sputnik V "has shown high efficacy" and was well tolerated for participants over 18 in final-stage clinical trials, said co-lead author Inna Dolzhikova of Russia's Gamaleya National Research Centre for Epidemiology and Microbiology.