Mask-wearing workers at a Pfizer factory in Michigan began packing the first shipments of its vaccine in dry ice early on Sunday.
Three trucks carrying pallets of boxed, refrigerated vaccines rolled away from the Kalamazoo facility at 8:29 am, escorted by body armour-clad security officers in a pickup truck and a SUV.
The United States expects to immunise 100 million people, or about 30% of its population, by the end of March, US Operation Warp Speed chief adviser Dr Moncef Slaoui said in an interview with Fox News.
In a novel process that will need to become daily routine, workers removed pizza-boxed sized cartons containing vaccine vials from a freezer.
They placed them in large, blue coolers, before these were boxed and labelled, as shown on a network television video feed.
The massive logistical effort is complicated by the need to transport and store the vaccine, developed with German partner BioNTech SE, at minus 70 Celsius, requiring enormous quantities of dry ice or specialised ultra-cold freezers.
Workers clapped and whistled as the first boxes headed to the trucks.
The long-awaited moment comes as the US death toll was approaching 300,000 and infections and hospitalisations set daily records.
It will take months before most US residents can get a COVID-19 vaccine.
The federal government plans to release the nation’s first 2.9 million doses to 64 states, US territories and major cities, as well as five federal agencies.
Although the federal government is coordinating distribution efforts, states have the final say over who gets the first shots. The federal government is sending the first shipments to more than 600 locations.