The keenly-awaited full results from a UK trial of the steroid dexamethasone has been published, confirming its life-saving benefits for Covid-19 patients on ventilators but suggesting it may cause harm if given too early.

A total of 2,104 hospitalised patients were assigned to receive six milligram daily doses of the medicine for up to 10 days, and 4,321 to receive usual care, with the rate of deaths compared after 28 days.

Among patients on ventilators, the rate of death for patients on the drug was 29.3pc compared to 41.4 per cent on those without. In other words, this group saw a 29pc reduction in mortality, just under a third.

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