The makers of Russia’s flagship Covid-19 vaccine said on Tuesday that interim results from phase 3 trials showed efficacy rates of “above 95 percent”, overperforming some of the most effective of the western vaccines that have released results. Moscow’s state-run Gamaleya Institute said data from nearly

19,000 volunteers showed the vaccine’s efficacy was 91.4 percent 28 days after they received the first dose of the two-shot jab, rising beyond 95 percent in preliminary results after 42 days.

The Kremlin is trumpeting the two-shot jab, known as Sputnik V after the Soviet satellite that kicked off the space race, as an alternative to vaccines from Moderna, Oxford University and AstraZeneca, and Pfizer/BioNTech.

Russia’s vaccine is the fourth in the past two weeks to show the efficacy of 90 percent or greater. None of these results have been confirmed by peer reviews. As a result, much hinges on what companies or institutions decide to disclose in press releases.

Countries including Saudi Arabia, Hungary, the UAE, Indonesia, the Philippines, Brazil, Mexico and India as well as former Soviet republics have registered interest in obtaining Sputnik V, while Russia said existing agreements would allow its partner countries to produce up to 500m doses of the vaccine next year.

But some experts have criticised Moscow’s rush to approve it and small sample sizes in its trials compared with western-made vaccines.