An announcement by Russia on Tuesday that it will approve a Covid-19 vaccine after less than two months of human testing prompted alarm among global health experts, who said that with no full trial data, the vaccine is hard to trust.

Intent on being first in the global race to develop a vaccine against the pandemic disease, Russia has yet to conduct large-scale trials of the shot that would produce data to show whether it works - something immunologists and infectious disease experts say could be a “reckless” step.