The first trial in people of a vaccine to protect against pandemic coronavirus is starting in the US later on Monday, according to reports.
A group of 45 healthy volunteers will have the jab, at the Kaiser Permanente research facility, in Seattle.
The vaccine cannot cause Covid-19 but contains a harmless genetic code copied from the virus that causes the disease.
Experts say it will still take many months to know if this vaccine, or others also in research, will work.
Scientists around the world are fast-tracking research.
And this first human trial, funded by the National Institutes of Health, sidesteps a check that would normally be conducted – making sure the vaccine can trigger an immune response in animals.
But the biotechnology company behind the work, Moderna Therapeutics, says the vaccine has been made using a tried and tested process.
This will hopefully prime the body’s own immune system to fight off the real infection.
The volunteers will be given different doses of the experimental vaccine.
They will each be given two jabs in total, 28 days apart, into the upper arm muscle.
But even if these initial safety tests go well, it could still take up to 18 months for any potential vaccine to become available for the public.