(CNN) Vaccinations against Covid-19 can now begin in the United States.
US Centers for Disease Control and Prevention Director Dr. Robert Redfield gave the final nod Sunday to the first coronavirus vaccine for the United States, clearing the way for shots to start.
Redfield accepted the recommendation of the agency's Advisory Committee on Immunization Practices that Pfizer and BioNTech's Covid-19 vaccine may be given to people 16 and older.
The first shots are expected to begin on Monday.
"This official CDC recommendation follows Friday's FDA decision to authorize the emergency use of Pfizer's vaccine. As COVID-19 cases continue to surge throughout the U.S., CDC's recommendation comes at a critical time," Redfield said in a statement.
"Initial COVID-19 vaccination is set to start as early as Monday, and this is the next step in our efforts to protect Americans, reduce the impact of the COVID-19 pandemic, and help restore some normalcy to our lives and our country."
The first freight trucks carrying approximately 184,275 vials of the vaccine departed Pfizer's facility in Kalamazoo, Michigan, on Sunday.
"They will begin moving vaccine from the Pfizer manufacturing facility to the UPS and FedEx hubs, and then it will go out to the 636 locations nationwide, which were identified by the states and territories," Gen. Gustave Perna, chief operating officer of Operation Warp Speed, told a news conference Saturday.
"We expect 145 sites across all the states to receive vaccine on Monday, another 425 sites on Tuesday, and the final 66 sites on Wednesday, which will complete the initial delivery of the Pfizer orders for vaccine," Perna added.
The shipments follow days of meetings and decisions by regulatory and public health officials.
The US Food and Drug Administration gave Pfizer and BioNTech's vaccine emergency use authorization on Friday, following a recommendation made Thursday by the agency's vaccine advisers.
"Science and data guided the FDA's decision," FDA Commissioner Dr. Stephen Hahn told a Saturday morning news conference.
"We believe that that transparency, as well as the rigorous scientific review that we've done, goes a long way to providing confidence and trust in the American people and FDA and this vaccine."
Following FDA's decision, CDC's vaccine advisers voted on Saturday to recommend that CDC approve the vaccine for use in the United States and add it to the vaccine schedule.
The CDC's OK on Sunday made those recommendations official.
During Saturday's meeting, ACIP members heard presentations about people's willingness to get the vaccine, who should and should not receive it, and how that will be communicated to health care providers and the general public.
ACIP members said Saturday that their evaluation of Pfizer and BioNTech's coronavirus vaccine was independent and transparent.
"I do believe that the process that we have used here in the ACIP to reach this decision is transparent, is science based, keeps equity in mind and is, for this moment, the absolute best that we can do," said ACIP member Dr. Beth Bell, a clinical professor of global health at the University of Washington.
Several committee members said they would get vaccinated, and would recommend it to their family members.
"I want to say that I voted for the vaccine because of the clear evidence of its efficacy/safety profile and benefit/risk profile, based on our evidence and policy framework," Dr. Peter Szilagyi, a pediatrician at the University of California Los Angeles and and ACIP member said immediately after the committee's vote.
Szilagyi said he wanted to emphasize the need for the federal government to spend substantially more to actually implement the recommendation.
"So this is government funding for state and local public health organizations, and also funding to health systems and health providers," Szilagyi said. "So I know we're going to have very tough and hard times ahead because of the surge and a limited vaccine supply, but I am really hopeful that this is the beginning of the end of the coronavirus pandemic."
Addressing the committee on Saturday, Dr. Nancy Messonnier, director of CDC's National Center for Immunization and Respiratory Diseases, said, "I know you share with me the burden of the importance of this moment."
Since the start of the pandemic, more than 16 million coronavirus cases have been diagnosed in the United States and nearly 300,000 people have been killed by the virus.
"There is much work left to do, but it's a hugely important step," Messonnier said.
"ACIP determined that COVID-19 is a major public health problem and that use of the Pfizer-BioNTech COVID-19 vaccine is a reasonable and efficient allocation of resources," the committee memebers wrote in a report issued by the CDC Sunday alongside Redfield's signoff.
"Whereas there might be uncertainty in how all populations value the vaccine, it was determined that for most populations, the desirable effects outweigh the undesirable effects."
Now the complex process of distributing the vaccines around the country gets underway.
Operation Warp Speed says it divided delivery in the United States between FedEx and UPS, which will transport vaccines to hospitals and pharmacies. About 2.9 million vaccines will head toward those first in line to for the shots: health care workers and residents of long-term care facilities.
The suitcase-sized containers carrying the Pfizer/BioNTech vaccine have already started to leave Pfizer's Michigan facility. They're packed with dry ice to keep the delicate vaccine at the extremely cold temperatures it requires.
The US Army general in charge of distributing America's first coronavirus vaccines said Saturday he's confident it will be done safely, even if it's not done perfectly.
"I am absolutely, 100% confident that we are going to distribute safely, this precious commodity, this vaccine needed to defeat the enemy, Covid," Operation Warp Speed's Perna said.
"Many of you want to know who will receive the first vaccine. And while I leave that up to the experts at the Health and Human Services organization, I remind you of this: Nearly 100,000 Americans have already rolled up their sleeves and participated in clinical trials across America. They were the true first recipients of the vaccine," Perna added.
"We'll be working hard the next couple days to ensure these first shipments go very well."