Video report by ITV News Science Editor Tom Clarke
British scientists have made the "biggest breakthrough yet" in the treatment of coronavirus with a drug which is "proven to reduce the risk of death", the prime minister has announced.
When trialled, the drug dexamethasone reduced the death rates of those on ventilators by around a third in comparison to the group given standard care.
He said he was "proud" of the "fantastic team of scientists right here in the UK" who conducted the "first robust clinical trial anywhere in the world" on the use of dexamethasone as a coronavirus treatment.
He thanked the thousands of patients in the UK who volunteered for the trials.
Sir Patrick Valance, the government's chief scientific adviser said the drug is cheap, meaning it can have effect worldwide.
"Dexamethasone is inexpensive, very widely available and the really exciting thing about this study is not only that it works, but it means that it can work across the world," he told the press conference.
But according to a government list of drugs from from export, dexamethasone had been banned in tablet form on April 24, and as an oral solution or for injection on June 16.
Prime Minister Johnson said he was "not aware" of the ban, adding it "sounds peculiar to me”.
England’s chief medical officer Professor Chris Whitty earlier said the dexamethasone trial “will save lives around the world”.
Patients given dexamethasone and who were not on a ventilator saw death rates drop by a fifth in comparison to standard care.
The risk of death was cut from 40 per cent to 28 per cent for patients on ventilators.
For those in need of oxygen, the risk of death was reduced from 25 per cent to 20 per cent.
There was no benefit, however, to patients who did not require respiratory support, the trial found.
Dexamethasone, a steroid which has been around for around 60 years, was trialled on around 2,104 patients and compared to 4,321 others who received standard care.
Peter Horby, leader of the RECOVERY trial, called their findings "a major breakthrough", while the Government's chief scientific adviser Sir Patrick Vallance said the results were "tremendous".
Professor Horby said the results of the trial were "really quite remarkable".
The University of Oxford academic who has led the dexamethasone trial, said his team’s efforts in the trial had “broken records”.
Speaking at the daily Downing Street briefing, he said: “In three months, we have enrolled over 11,500 patients and this makes it by far the biggest clinical trial in the world.”
He said the majority of patients being treated in hospital for coronavirus were likely to benefit from the study into dexamethosone, after conducting a trial comparing 2,000 people being treated with the drug and 4,000 without.
During the trial, which concluded on June 8, patients received a low dose of 6mg per day by mouth or injection for 10 days.
The prime minister said the drug would now be available across the NHS and “we have taken steps to ensure we have enough supplies, even in the event of a second peak”.
Mr Johnson is speaking after allowing a major policy U-turn on free meals for children during the summer holidays following pressure piled on by Marcus Rashford's campaign.
Mr Johnson said he had spoken to England striker Rashford to “congratulate him” on his campaign for free school meals over the summer, adding: “I thank him for what he’s done.”
His appeal for an extension to the free school meal voucher scheme through the summer holidays had been dismissed despite increasing pressure from public figures and politicians.
But now the government says it will set up a summer food fund for those who would usually receive free school meals during term time.
Mr Johnson's spokesperson said the plan to provide around 1.3 million children in England with a six week food voucher will cost £120 million.
The coronavirus update follows the announcement that the Department for International Development is to be scrapped in a merger with the Foreign Office.
Watch Boris Johnson's press conference in full: