The first human trial of a vaccine to protect against pandemic coronavirus has started in the US.
Four patients received the jab at the Kaiser Permanente research facility in Seattle, Washington, reports the Associated Press news agency.
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.
The first person to get the jab on Monday was a 43-year-old mother-of-two from Seattle.
"This is an amazing opportunity for me to do something," Jennifer Haller told AP.
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.
