US pharmaceutical company Pfizer and German company BioNTech's COVID-19 vaccine was being loaded onto trucks on Sunday at a Michigan plant.
The vaccine was authorised for emergency use in the United States on Friday.
An assembly line of workers pulled doses of the vaccine out of a freezer to box it up and put it on trucks to be distributed throughout the country from Monday.
Dry ice, shipping labels and packing tape were on hand as workers in face masks and gloves prepared the packages.
About three million doses of the vaccine are being sent out initially for healthcare workers and nursing home residents.
Infections, hospitalisations and deaths have risen recently in the United States and it's expected to get worse over the holidays.