The US government is expected to approve the Pfizer COVID-19 vaccine for emergency use within hours, according to reports.
If the Food and Drug Administration (FDA) signs off on the jab created by the German company BioNTech, it would pave the way for the biggest vaccination campaign in US history to start within days.
Full, non-emergency approval is expected to follow sometime next year.
Coronavirus has killed nearly 300,000 people in the US so far, with infections still surging in the country.
On Thursday, a US government advisory group voted 17-4 in favour of approving the jab for emergency use for those aged 16 years and older, clearing the way for the FDA to give the vaccine the green light.
How COVID-19 vaccines ordered by the UK compare
The Pfizer/ BioNTech vaccine was developed at unprecedented speed, less than a year after COVID-19 was identified.
It requires two doses, three weeks apart to work. It must be stored at -70C and is 95% effective.
Millions of doses will now be sent out to begin vaccinating healthcare workers and nursing home residents, however widespread access to the American public is not expected until the spring.
The UK was the first country in the world to approve the vaccine, followed by Bahrain and Canada.