6 monkeys given an experimental coronavirus vaccine from Oxford did not catch COVID-19 after heavy exposure, raising hopes for a human vaccine

• Macaque monkeys given a experimental vaccine from the University of Oxford appear to have resisted the coronavirus.
• Six macaques given hAdOx1 nCoV-19 at in Montana did not fall ill, despite heavy exposure.
• There is no guarantee the vaccine will work on humans, but successful animal tests are a promising early sign.
• The Oxford Vaccine Group began human trials for the vaccine last week.
• Visit Business Insider's homepage for more stories.

Six macaque monkeys given a trial vaccine from the University of Oxford are coronavirus-free 28 days after sustained exposure to the virus.

The result is a promising early sign for the vaccine, which is also undergoing human trials. However, a working human version remains months away even in the best-case scenario.

The monkey experiment was carried out in late March by government scientists at the Rocky Mountain Laboratories in Hamilton, Montana, The New York Times reported.

A control group of six macaques was exposed to the virus and fell ill.

Six other macaques were also exposed, but after receiving a vaccine produced by The Jenner Institute and the Oxford Vaccine Group. They suffered no ill effects, and remain healthy 28 days later, the Times said.

"The rhesus macaque is pretty much the closest thing we have to humans," Vincent Munster, the head of the Virus Ecology Unit at the laboratory, told the Times.

The Jenner Institute, working as part of the Oxford Vaccine Group, is leading the global race for a coronavirus vaccine. The UK government has pledged £20 million ($25 million) to the trial.

The vaccine given to the macaques is called hAdOx1 nCoV-19. Human trials began on April 23, but are expected to be finished until September. The process of developing a vaccine is long, and even having a usable product by September would be unusually fast.

On Monday the world's largest vaccine maker, the Serum Institute of India, said it would not wait for the trial to end, and is pre-emptively making 40 million doses to save time in case it works.

Sinovac Biotec, a Beijing-based company is also hunting for a vaccine to the coronavirus. It found last week that its vaccine was also effective in macaques. Human trials have now begun.

Humans and macaques share about 93% of their DNA. However, just because a vaccine appears to work on the macaque it does not mean it will work on humans.

As many as 80 vaccines are currently in development, but some are choosing to skip the animal testing stage to save time.