Two early-phase Russian coronavirus vaccine trials have produced promising results, with participants experiencing no serious adverse effects and evidence of an antibody response.

Controversy greeted the announcement last month that Russia had approved the worlds first Covid-19 vaccine before it had completed final phase 3 clinical trials.

Those still have not been done. But the findings of two smaller 42-day trials published in the Lancet medical journal on Friday do suggest the vaccines produce a double protection in the form of a T-cell response within 28 days.

T-cells attack viruses directly by recognising and killing cells that have been taken over by a virus.