Russia stopped taking in new volunteers in the trial of its first vaccine against Covid-19 on Wednesday, with developers saying it was unethical to administer a placebo to participants now that the shot was increasingly available to the public.

Russia began rolling out the Sputnik V vaccine as part of a national inoculation programme in early December as the final, phase III trial continued in the capital at the same time.

Now the trial will be cut short, with only 31,000 volunteers taking part rather than the planned 40,000, the Health Ministry said in a statement...