The first shipments of the BioNTech-Pfizer vaccine were sent out to distribution centers across the United States on Sunday.
It was the first step in a massive COVID vaccine rollout in the world's worst-hit country — with vaccinations expected to begin on Monday.
Workers at a Pfizer factory in the city of Kalamazoo, Michigan, packed the first shipments of the vaccine in boxes layered with dry ice.
Refrigerated trucks carrying the first shipments were escorted to a nearby airport by security officers wearing body armor.