The first shipments of the COVID-19 vaccine set to be distributed to all 50 states in the US left Pfizer's facility in Kalamazoo, Michigan, on Sunday morning, at a pivotal moment in the pandemic which has killed nearly 300,000 Americans.

The shipments, that are expected to reach every state on Monday, began two days after the Food and Drug Administration authorized emergency use of the Pfizer-BioNTech vaccine following an overwhelming 17–4 vote of confidence from an advisory panel of independent experts.

The first shipments of the vaccine are expected to arrive at 145 distribution sites across the US on Monday, federal officials said. Another 425 sites will receive shipments on Tuesday, and the remaining 66 will get them on Wednesday.

The vaccine offers much-needed hope in battling what has been a devastating crisis for the US, even as the country approaches a grim milestone and is bracing for what public health experts have predicted is going to be a very difficult winter.

Photos and videos provided an inside look at Pfizer's workers carefully packing up the vaccines and loading them on to the trucks at the facility early Sunday morning.

The two freight trucks departing from Pfizer's facility were carrying around 184,275 vials of the vaccine with healthcare workers and nursing home residents first in line to get the shots. There are five doses of vaccine per vial. Pfizer workers are preparing to ship out an additional 3,900 vials later on Sunday, while 390,000 vials will be shopped on Monday, CNN reported.

Workers at Pfizer's facility on Sunday morning took a moment to clap for the historic moment as the first boxes of the vaccine were being loaded on to the trucks.

The vials were stored in containers filled with dry ice to ensure that they will remain at -94 degrees Fahrenheit — as the vaccine's mRNA molecules break down at room temperature.

The trucks carrying the first shipments of the vaccine were escorted by the US Marshal's Service.

 People cheered as the trucks carrying the first shipments of the COVID-19 vaccine left Pfizer's Global Supply facility in Kalamazoo, Michigan, on Dec. 13.

A UPS worker hooks a truck to a trailer containing shipments of the vaccine at the Capital Region International Airport in Lansing, Michigan, on Dec. 13.

Shipments of the vaccine are loaded into a UPS plane at the Capital Region International Airport on December in Lansing, Michigan.

FedEx and UPS said Sunday that the vaccine shipments had arrived at their central facilities from where they will delivered to distribution sites such as hospitals and other centers that have the capability to store the vaccines at the required temperature.