The backers of the Russian Covid-19 vaccine Sputnik V said Monday that the jab is effective against the new 'Omicron' coronavirus variant but they were also developing an adapted booster.

The Russian Direct Investment Fund (RDIF), which supported the vaccine's development by the state-run Gamaleya Center, said that the centre "has already begun developing the new version of Sputnik vaccine adapted to 'Omicron'."

"In an unlikely case such modification is needed, the new Sputnik 'Omicron' version can be ready for mass-scale production in 45 days," RDIF said in a statement.

"Several hundred million Sputnik 'Omicron' boosters can be provided to international markets already by February 20, 2022 with over 3 billion doses available in 2022."

The promise comes after the US pharmaceutical company Moderna said Friday that it will develop a booster shot against the highly mutated strain of the coronavirus, which is more transmissible than the dominant Delta variant.

Germany's BioNTech and US drugmaker Pfizer said the same day that they expect data "in two weeks at the latest" to show if their jab can be adjusted.

Last week RDIF said Sputnik V provides longer immunity against the coronavirus than Western jabs using messenger RNA (mRNA) technology.

It added that the Sputnik vaccine is 80 percent effective against the coronavirus between six and eight months after the second dose.

No independent study has confirmed the claim.

Russia registered Sputnik V last August ahead of large-scale clinical trials, prompting concern among experts over the fast-tracked process.

But it was since declared safe and over 90 percent effective in a report published by leading medical journal The Lancet.

The RDIF says its two-dose vaccine has been approved in 71 countries and that it has applied for registration in the European Union.

Earlier this summer several Latin American countries that have relied on the Russian vaccine to protect their populations complained to Moscow about delivery delays.