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MEMPHIS, Tenn. — A shipment of a COVID-19 vaccine touched down at FedEx’s world hub in Memphis around noon on Sunday.

The vaccines will go from FedEx and UPS hubs around the country to be delivered to 636 pre-determined locations nationwide, with 145 of those sites should receive the vaccine by Monday with other sites getting the vaccine by Wednesday.

The touchdown in Memphis came shortly after the first shipments of Pfizer’s COVID-19 vaccine are being loaded up and moved out from Pfizer’s Michigan headquarters.

The first shots expected to be given in the coming week to health care workers and at nursing homes.

Shipments of the Pfizer vaccine will set in motion the biggest vaccination effort in American history at a critical juncture of the pandemic that has killed 1.6 million and sickened 71 million worldwide.

Initially, about 3 million doses were expected to be sent out, and the priority is health care workers and nursing home residents as infections, hospitalizations and deaths soar in the U.S. With numbers likely to get worse over the holidays, the vaccine is offering a bright spot in the fight against the pandemic that’s killed nearly 300,000 Americans.

The vials are initially stored in the freezer area where the vaccine is kept at temperatures hovering around negative 94 degrees Fahrenheit or negative 70 degrees Celsius.

Workers at Pfizer in Michigan started rolling bins and moving vaccines from the freezer farm into coolers packed with dry ice.

From there, the vials are moved on to a belt and packed with more dry ice until it’s moved out to the loading dock.

Workers paused for a moment and started to clap as the first boxes of vaccine were being moved to a loading dock. (See video above)

Pfizer — the maker of the vaccine — has confirmed to NBC News that all 50 states will receive some portion of the first round of shipments.

The Food and Drug Administration authorized the use of Pfizer’s COVID-19 vaccine late last Friday night. An estimated 2.9 million doses will be distributed within a week.

That number will ramp up to as many as 40 million doses by the end of the year. In addition to the Kalamazoo location, Pfizer is currently using two other manufacturing sites to produce the vaccine.

Pfizer and its partner BioNTech say based on current projections, they believe they could potentially supply up to 1.3 billion doses by the end of next year.

The company says it supplied vaccine to over 150 clinical trial sites around the world, reaching about 44,000 participants.