The nation's first COVID-19 vaccine have began arriving across the United States Monday morning, after the government gave the final go-ahead to the shots needed to end an outbreak that has killed nearly 300,000 Americans. U.S. Army Gen. Gustave Perna, who heads the Trump administration's Operation Warp Speed said: "We wanted to get out to American people right away." He confirmed that off an initial 145 shipments of vaccines, "we know that 55 have been received and we'll track the remaining 95 accordingly." Trucks rolled Sunday morning as shipping companies UPS and FedEx begin delivering Pfizer's vaccine to nearly 150 distribution centers across the states. "We face very challenging trends across the country," Health and Human Services Secretary Alex Azar told reporters Monday, "as the virus continues to spread, with hospitalizations and deaths are near record highs in many places and still rising." "But today we have hope on the way," Azar said. Initially, about 3 million doses were expected to be shipped nationwide. It was unclear exactly who would receive the first shots, though health care workers and nursing home residents were the priority. Perna said health authorities would decide. A similar number of shots will be held back for those recipients' second dose, which is needed for full protection from COVID-19. A weekend announcement kicked off a massive logistical operation involving the federal and state governments, private companies and health care workers to quickly distribute limited vaccine supplies throughout the U.S. It offers hope in a country grappling with surging COVID-19 infections and deaths, which are overwhelming hospitals and raising fears that things will only get worse as people gather over the holidays. The Food and Drug Administration authorized emergency use of the vaccine late Friday. It capped an unprecedented global race to speed vaccines through testing and review, chopping years off the normal development process. The FDA found the vaccine highly protective with no major safety issues. U.S. regulators worked for months to emphasize the rigor and independence of their review, but President Donald Trump's administration pressured the agency until the final announcement. A top White House official even threatened to remove FDA chief Stephen Hahn if a ruling didn't come before Saturday. The FDA will review a vaccine from Moderna and the National Institutes of Health that appears about as protective as Pfizer's shot.