The steroid dexamethasone was shown Tuesday to be the first drug to significantly reduce the risk of death among severe COVID-19 cases, in trial results hailed as a “major breakthrough” in the fight against the disease.

Britain’s Health Secretary Matt Hancock said the country’s patients would start to receive the drug immediately.

Hancock said the government had started stockpiling dexamethasone back in March after preliminary trials showed “early signs” of the drug’s potential.

Researchers led by a team from the University of Oxford administered the widely available drug to more than 2,000 severely ill COVID-19 patients.

Among those who could only breathe with the help of a ventilator, dexamethasone reduced deaths by one third, and by one-fifth in other patients receiving oxygen only, according to preliminary results.

Normally used to treat a range of allergic reactions as well as rheumatoid arthritis and asthma, dexamethasone is an anti-inflammatory.

Daily doses of the steroid could prevent one-in-eight ventilated patient deaths and save one out of every 25 patients requiring oxygen alone, the team said.

The trial, carried out by the RECOVERY research group that is searching for effective COVID-19 treatments, included a control group of 4,000 patients who did not receive the drug.

“Dexamethasone is the first drug to be shown to improve survival in COVID-19. This is an extremely welcome result,” said Peter Horby, professor of Emerging Infectious Diseases in the Nuffield Department of Medicine, University of Oxford.

“Dexamethasone is inexpensive, on the shelf, and can be used immediately to save lives worldwide.”

The trial results are particularly promising as around 40 per cent of COVID-19 patients who require a ventilator end up dying, often because of the body’s uncontrolled inflammatory response to the virus.

For those receiving the new treatment, the mortality rate dropped to less than 30 percent.

“This is a major breakthrough: dexamethasone is the first and only drug that has made a significant difference to patient mortality for COVID-19,” said Nick Cammack, COVID-19 therapeutics accelerator lead at the Wellcome Trust health charity.

“Potentially preventing one death in every eight ventilated patients would be remarkable.”