President Vladimir Putin says his own daughter has already received it, but testing is yet to be completed and experts are skeptical about how quickly the vaccine has been registered.

While details about the research behind the vaccine are limited, here's what we know so far.

What do we know about the Russian vaccine?

The vaccine was developed by the Moscow-based Gamaleya Institute, using funding from the Russian Direct Investment Fund (RDIF). The vaccine is named Sputnik V -- a reference to the 1957 Soviet Union satellite.

Scientists conducted months of human trials but are yet to publish data and did not begin the crucial Phase 3 stage, which usually precedes approval, before the announcement on Tuesday.

On Wednesday it was announced that a Phase 3 trial involving more than 2,000 people in Russia and several Middle Eastern and Latin American countries had begun. Typically this stage of trial involves testing on tens of thousands of people.

Dr. Scott Gottlieb, former commissioner of the US Food and Drug Administration (FDA), said Tuesday that the number of people the vaccine had been tested on so far was the equivalent of a Phase 1 trial, which typically involves a small group and studies the safety of the vaccine.

Is the Russian vaccine safe?

The short answer is that we don't know. Russia has released no scientific data on its vaccine testing and CNN is unable to verify claims about its safety or effectiveness. But Russia says the vaccine has passed through Phase 1 and Phase 2 trials which were completed on August 1.

A Phase 1 study typically focuses on whether a vaccine is safe and whether it elicits an immune response in a small number of people.

"We do not have any information whatsoever on whether this is safe," Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases, University of Nottingham, told CNN.

Russia claims that volunteers in the Phase 1 and 2 trials felt well after taking the vaccine, and exhibited no unforeseen or unwanted side effects.

Neal said that researchers were unlikely to have detected any rare side effects linked to the Gamaleya vaccine.

"You won't know about side effects without [widespread] testing, if they're rare. That's the point of a Phase 3 study," he said.

"I wouldn't take it, certainly not outside of a clinical trial right now," Gottlieb told CNN Tuesday.

Is the vaccine effective?

Without data and completed Phase 3 trials, Russia has not proven to the world Sputnik V works.

"I would think that it at least produces antibodies. What we don't know is if it protects people against infection," Neal told CNN.

Russia has said that its vaccine is an adenoviral vector one. Adenoviruses cause the common cold, but in Covid-19 vaccines they're weakened and modified to deliver genetic material that codes for a protein from the novel coronavirus.

The body then produces that protein and may produce an immune response against it but the method can cause problems.

Sputnik V's makers say the vaccine induced a "strong antibody and cellular immune response," in trial