If the ZD1222 vaccine is to be effective, it could allow people to leave their homes, go back to work, and rebuild the economy.
But Professor Adrian Hill, director of the university’s Jenner Institute, revealed that his team now faces a major problem, throwing the September deadline into doubt.
Professor Hill who is in charge of the development of the vaccine at Oxford University said he needed 10,000 infected people to prove the effectiveness of the cure.
However, coronavirus is disappearing so rapidly in the UK that the next phase of trials has only a 50 percent chance of success.
Without the virus spreading in the community, volunteers will not catch the disease, leaving scientists unable to prove that their vaccine makes any difference.
Meanwhile Boris Johnson is to hold a Cabinet meeting of his senior ministers on Monday to discuss ways in which the UK can further ease lockdown restrictions.
This will likely include an update on the reopening of schools and possibly non-essential retail.
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9.20am update: Thailand on Sunday reported no new coronavirus cases and no new deaths.
There was a total of 3,040 confirmed cases and 56 fatalities in the country since the outbreak began in January.
8.50am update: Singapore has confirmed 548 more coronavirus cases, taking its tally to 31,616.
To date there have been 23 deaths from Covid-19 in the country.
8.05am update: Coronavirus cases in Brazil near 350,000.
Brazil registered 965 new coronavirus deaths on Saturday, taking the total number of fatalities to 22,013, the Health Ministry said.
The country now has 347,398 confirmed cases, according to the ministry, up 16,508 from Friday, when it surpassed Russia to become the world’s virus hot spot behind the US
7.45am update: The Wuhan pathogen laboratory that is at the centre over speculation about a coronavirus lab-leak had bat strains of the coronavirus, but not Covid-19, Chinese scientists say.
The virology lab in Wuhan, the city at the heart of the outbreak, was working on three live strains of bat coronavirus, but none of them match the one that has caused the Covid-19 pandemic, its director has said.
Wang Yanyi told Chinese state broadcaster CGTN: “Our institute first received the clinical sample of the unknown pneumonia on December 30 last year. We didn’t have any knowledge before that, nor had we ever encountered, researched or kept the virus. In fact, like everyone else, we didn’t even know the virus existed. How could it have leaked from our lab when we never had it?”