Why it matters: Scientists around the world are skeptical about Russia’s claims. There is no published scientific data to back up Putin’s claims that Russia has a viable vaccine — or that it produces any sort of immunity without significant side effects.

A Russian vaccine has not gone through any phase three trials, which are lengthy and involve thousands of participants for testing.

Experts caution that introducing a vaccine to the population without widespread testing could have serious negative consequences, including unexpected side effects or simply undermining public trust in their efficacy.