Americans will start receiving the Pfizer-BioNTech Covid-19 vaccine on Monday, the official in charge of the distribution operation said today.
General Gustave Perna told reporters the first doses will be shipped tomorrow.
"We are operationally 100% confident that we will get the vaccines to the American people [starting Monday morning]," he said.
"Expect 145 sites across all the states to receive vaccine on Monday, another 425 sites on Tuesday. And the final 66 sites on Wednesday, which will complete the initial delivery of the Pfizer-BioNTech vaccine," he said.
The first push will vaccinate about three million people.
Federal health authorities have recommended that health care workers and nursing home residents be at the front of the line, but the decisions will be left to individual states.
The US became the sixth country to green light the Pfizer vaccine last night after Britain, Bahrain, Canada, Saudi Arabia and Mexico.
It has been shown to be 95% effective in preventing Covid-19 infection compared to a placebo.
But the Food & Drug Administration (FDA) has advised people who have severe allergies to ingredients in the drug to avoid getting immunised for the time being.
President Donald Trump immediately released a video on Twitter, where he hailed the FDA's approval of the vaccine.
— Donald J. Trump (@realDonaldTrump) December 12, 2020
The roll-out decision comes as infections in the world's worst-hit country soar as never before, with the grim milestone of 300,000 confirmed deaths fast approaching.
It was widely reported in the US media that the White House had threatened to fire FDA chief Stephen Hahn if he did not issue the Emergency Use Authorisation (EUA) within hours.
Mr Hahn disputed the reporting but nonetheless gave the order, which was previously not expected until later in the weekend or early next week.
The US will now undertake a complex logistical operation to ship millions of doses out to hospitals, clinics, pharmacies and long-term care facilities across the country.
The distribution is being overseen by General Gustave Perna as part of Operation Warp Speed, but handled by private sector partners like FedEx who are using special boxes to manage the vaccine's cold storage requirement of -70 degrees Celsius.
The decision is a win not just for American pharmaceutical giant Pfizer and its smaller German partner BioNTech, but also for the mRNA (messenger ribonucleic acid) technology the vaccine is based on.
Traditional vaccines normally rely on using weakened or inactivated forms of disease-causing microbes.
The new technology delivers genetic instructions to human cells to make them express a surface protein of the SARS-CoV-2 virus.
This simulates an infection and prepares the immune system in case it encounters the real virus.
Developing these vaccines is faster than more traditional approaches. But their main drawback is that mRNA molecules, which are encased in fatty particles, have to be stored at ultra cold temperatures.
The US hopes to vaccinate 20 million people this month, counting on a second vaccine, developed by Moderna and the National Institutes of Health, to come through next week.
This second vaccine is also based on mRNA.
Healthcare workers and long-term care facility residents are at the front of the line.
