Putin lauds AstraZeneca as it signs vaccine tie-up deal with Russia

* Trials to test combining two vaccines to start soon

* Putin praises AstraZeneca for cooperation

* Belarus to start producing Russian Sputnik V vaccine

* Russia believes Sputnik effective against new virus strain

By Andrew Osborn and Vladimir Soldatkin

MOSCOW, Dec 21 (Reuters) - Russian President Vladimir Putin on Monday hailed British drugmaker AstraZeneca's decision to test combining its own experimental COVID-19 vaccine with Russia's Sputnik V shot, as Moscow said the start of clinical trials was imminent.

Putin was speaking by video conference at a virtual event that saw AstraZeneca sign a memorandum of cooperation with Russia's Gamaleya Institute, which developed Sputnik V, Russia's RDIF sovereign wealth fund, and Russian drugmaker R-Pharm.

Clinical trials, still under way, have shown Sputnik V has an efficacy rate of over 90%, higher than that of AstraZeneca's own vaccine and similar to those of U.S. rivals Pfizer and Moderna.

Putin praised Pascal Soriot, AstraZeneca's chief executive, who had dialled in by video conference.

"I want to single out your pro-active stance to achieve goals that are highly important, not just for your company, but in reality and without excessive bombast or exaggeration, for humanity," said Putin.

Kirill Dmitriev, the head of RDIF, told the event that clinical trials combining the Russian and British vaccines would start soon in three countries.

He did not name the countries, but mentioned some of them were in the Middle East and the former Soviet Union.

Dmitriev has previously said Russia believes the combination will boost the efficacy of the AstraZeneca vaccine.

Kate Bingham, chair of Britain's vaccine task force, said this month the UK would start trials next year using combinations of different kinds of vaccine for the initial and booster vaccinations, in the hope that a "mix-and-match" approach might maximise the immune response.

The cooperation between one of Britain's most valuable listed companies and the state-backed Russian research institute highlights the pressure to develop an effective shot to fight the pandemic, which has killed over 1.6 million people.

In Moscow, the move is seen as a long-awaited vote of confidence by a Western manufacturer in Sputnik V, which Russian authorities say is the target of a foreign-backed smear campaign.

Russia wants to produce the new vaccine jointly if it is proven to be effective.

Dmitriev, head of RDIF, which has financed and promoted Sputnik V, also announced on Monday that Russia believed Sputnik was highly effective against a new strain of the coronavirus found in Europe.

He said neighbouring Belarus would begin producing the Russian vaccine in the first quarter of next year and that Kazakhstan had started production.

Foreign manufacturing facilities would produce more than 500 million doses of the Russian vaccine next year, said Dmitriev. (Editing by Mark Potter)