Top US health expert Fauci said he really doubted that Russia's Sputnik V vaccine is safe and effective.

"I hope that the Russians have indeed proven the vaccine to be safe and effective. I really doubt whether they have done that," White House medical advisor Anthony Fauci said in an interview with ABC today.

Getting a vaccine and proving it safe and effective are two completely different things, says Fauci.

"If we want the chance to injure a lot of people or give them something that doesn't work, we can start right away, next week if we want to. However, that's not how we do it."

The epidemiological expert added that Russia or China have vaccines that are completely different from vaccines produced in the US.

President Vladimir Putin announced on the same day that Russia had successfully developed the first vaccine providing "strong immunity" against Covid-19 after less than 2 months of human testing.

Health officials in the US and Germany immediately expressed skepticism about the safety of the vaccine due to lack of data and the trial has not yet been completed.

The world has mobilized an unprecedented amount of funding and research to quickly develop vaccines that can protect people from Covid-19.