The calculations of its effectiveness were based on preliminary data obtained 42 days after the first dose, Russia’s health ministry, the state-run Gamaleya research centre and the Russian Direct Investment Fund (RDIF) said in a statement.

The statement said that the vaccine had shown 91.4 per cent effectiveness 28 days after the first dose, a figure based on 39 cases.

Forty-two days later, after a second dose, data showed “an efficacy of the vaccine above 95 per cent”.

It did not note the number of coronavirus cases used to make the final calculation, however.

“The second analysis was conducted a week after volunteers got the second dose, meaning that their bodies have partially reacted to both doses,” Gamaleya’s director Alexander Gintsburg said in the statement.

He said the centre expects the efficacy rate to be “even higher” three weeks after the second dose.

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The statement said that 22,000 volunteers had been vaccinated with the first dose and more than 19,000 with both doses.

Overseas trials of the vaccine are also taking place in the United Arab Emirates, Venezuela, Belarus and other countries.

Russia in August became the first country to register a coronavirus vaccine but did so ahead of the large-scale clinical trials that are still under way.

Last month, President Vladimir Putin announced that Russia had registered a second coronavirus vaccine, EpiVacCorona, as a global race heats up in producing an effective vaccine to combat the pandemic, which has now claimed the lives of nearly 1.4 million people.

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Putin last week said that Russia had manufacturing agreements in place with China and India and encouraged Brazil and South Africa to also mass produce Russian-made vaccines.

Pharma giants Pfizer and BioNTech announced that their virus vaccine is 95 per cent effective, while US company Moderna said last week early results showed its candidate was 94.5 per cent effective.

Meanwhile, the European Commission has reached a deal with US biotech firm Moderna for the supply of its vaccine candidate, an EU official said on Tuesday.

Last week Moderna said its experimental vaccine was 94.5 per cent effective in preventing Covid-19, based on interim data from a late-stage clinical trial.

In August the Commission, which co-leads talks with vaccine makers on behalf of EU states, said preliminary talks with Moderna had been concluded with the aim of signing a contract for the supply of 80 million doses of its vaccine, with the option of buying another 80 million.

Additional reporting by Reuters