The first shipments of Pfizer’s COVID-19 left a Michigan factory on Sunday, kicking off a historic effort to stop a surging pandemic that is claiming the lives of more than 2,400 Americans a day.

Mask-wearing workers at a Pfizer factory in Kalamazoo began packing up the vaccine in dry ice early Sunday morning and loaded the first shipments onto trucks bound for FedEx and UPS planes that will whisk the precious cargo across the country.