Americans could start receiving a COVID-19 vaccine as early as 11 December, according to the chief scientific adviser for the US government's vaccine programme.
Dr Moncef Slaoui, part of Operation Warp Speed, told NBC: "Within 24 hours from the approval, the vaccine will be moving and located in the areas where each state will have told us where they want the vaccine doses."
There were no serious safety concerns observed in those who took part in the trials, with the vaccine tested on people with and without a prior coronavirus infection.
The US Food and Drug Administration's outside advisers will meet on 10 December to discuss whether to authorise the vaccine for emergency use.
This would mean it could be used for those who are at highest risk from the virus and Dr Slaoui said it would be distributed based on each state's population.
States would decide how to prioritise groups but it would be recommended that healthcare workers be vaccinated first, along with other front-line workers and the elderly.
Dr Slaoui said about 70% of the population needs to be immunised to achieve herd immunity and this would be possible by May.
But there are concerns that uptake of any vaccine could be low, due to misinformation and a well-established network of anti-vaxxers in the country.
More than 12 million people in the US have been confirmed to have had the virus, with almost 260,000 having died.
The UK has already ordered enough of the Pfizer vaccine candidate to vaccinate 20 million people but it has not yet been approved by the Medicines and Healthcare Products Regulatory Agency.
Pfizer and BioNTech expect to produce up to 50 million doses globally in 2020 and up to 1.3 billion doses by the end of 2021.