Scientists have moved a step closer to developing a coronavirus vaccine during the animal testing phase during tests on monkeys.
Scientists at Oxford University injected six rhesus macaque monkeys with a vaccine.
Four weeks after being exposed to the virus the monkeys remain free from infection.
The success means that a human trial with 6,000 participants will begin by the end of May, reports The New York Times.
Despite monkeys not involved in last month's trial in Montana becoming sick, all half dozen participants showed no signs of Covid-19 after being given the vaccine.
If all goes well, the new vaccine would be granted emergency approval by authorities and lead to 'millions' of doses available by September, it is claimed.
Lead researcher Dr Vincent Munster for the National Institutes of Health's Rocky Mountain Laboratory said the species of monkey used is "the closest thing we have to humans".
There is no guarantee the vaccine will work on humans but Dr Munster plans to submit his research to a peer-reviewed journal.
As many as 100 potential COVID-19 candidate vaccines are now under development by biotech and research teams around the world, and at least five of these are in preliminary testing in people in what are known as Phase 1 clinical trials.
Last week, the first human trial in Europe of a coronavirus vaccine begun in Oxford.
Two volunteers were injected, the first of more than 800 people recruited for the study.
Italy's ReiThera, Germany's Leukocare and Belgium's Univercells said they were working together on a potential shot and aimed to start trials in a few months.
Britain's GSK and France's Sanofi last week announced a similar agreement to develop a COVID-19 vaccine, with trials starting in the second half of the year.
The race for a vaccine has been fueled by the shortage of options for treating the disease.
Mylan NV, Teva Pharmaceutical Industries and Amneal Pharmaceuticals Inc are ramping up production of their own versions of malaria drug hydroxychloroquine, which is being tested in multiple clinical trials against the coronavirus.
Novartis and Bayer AG have said they will donate their own versions of that drug.
The European Union's drug regulator on Thursday reiterated a warning against using two older malaria drugs outside of trials or national emergency use programs, citing potentially lethal side effects.
