Washington D.C. – Medical workers are due to give the first doses of the Pfizer/BioNTech coronavirus vaccine in locations across the United States on Monday, kicking off the largest inoculation program in the country's history.

Regulators over the weekend gave the final approvals needed for the emergency use of the vaccine, and logistics companies working with the federal government began to move the doses from Pfizer's sites to distribution points.

Among the first in line to get the available doses will be health care workers at high risk.

About 145 sites in all 50 states will get doses on Monday, with hundreds more during the days ahead, according to the US military, which is helping with the logistics.

Health and Human Services Secretary Alex Azar will preside over a ceremony at George Washington University Hospital in Washington D.C. to mark the event, but states will be administering their own programs over the course of the day and in the weeks ahead.

The first vaccines are being rolled out as the US nears the grim death toll of 300,000 people from the virus. The country has been regularly breaking its daily records for hospitalizations from Covid-19, in a sign of an ongoing serious outbreak.

Los Angeles' LAX airport was among the logistical nodes that confirmed that the vaccines were moving to their final destinations, posting photos on Twitter of FedEx planes landing, doses on board.

Governors and officials in numerous states also confirmed their health authorities were in possession of the doses.