• President-elect Joe Biden on Tuesday criticized the Trump administration's effort to distribute and administer Covid vaccine shots.
• "The Trump administration's plan to distribute vaccines is falling behind, far behind," he said at a news briefing.
• He added that his administration will "set up vaccination sites and send mobile units to hard to reach communities" to accelerate the pace of vaccinations.

President-elect Joe Biden on Tuesday criticized the Trump administration's effort to distribute and administer Covid vaccine shots, saying that the administration has failed to meet its own goals.

"The Trump administration's plan to distribute vaccines is falling behind, far behind," he said at a news briefing. "As I long feared and warned, the effort to distribute and administer the vaccine is not progressing as it should."

He said his administration will "move heaven and earth" to accelerate the distribution and administration of the Covid vaccines once he takes office on Jan. 20. He reiterated his administration's pledge to have administered 100 million doses of vaccine by his 100th day in office.

To meet that goal, Biden said, it "would take ramping up five to six times the current pace to 1 million shots a day." He said his team will act more aggressively to increase administration of the shots, but even at 1 million per day, it will take months to vaccinate the majority of the population.

"This is going to be the greatest operational challenge we've ever faced as a nation," he added. "We're going to get it done. It's going to take a vast new effort. It's not yet underway."

Biden said his administration will also invoke the Defense Production Act, a wartime law that enables the president to compel companies to prioritize manufacturing for national security, to ensure manufacturers have enough materials needed for vaccine production. He said he will also use the authority to expand production of personal protective equipment like masks.

He added that his administration will "set up vaccination sites and send mobile units to hard to reach communities."

While more than 11.4 million vaccine doses had been distributed to states as of Monday, just over 2.1 million doses had been administered, according to the Centers for Disease Control and Prevention. The agency notes that its data might lag the actual number of doses administered as states and jurisdictions report up the data.

"A large difference between the number of doses distributed and the number of doses administered is expected at this point in the COVID vaccination program due to several factors, including delays in reporting of administered doses, management of available vaccine stocks by jurisdictions, and pending launch of vaccination through the federal Pharmacy Partnership for Long-Term Care Program," the agency said on its vaccine tracking site.

Representatives for the CDC did not return CNBC's request for further comment on the disparity between doses administered and doses distributed.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, acknowledged Tuesday on CNN that the vaccine rollout has been slower than anticipated.

"We certainly are not at the numbers that we wanted to be at the end of December," he said in an interview with Jim Sciutto. "I believe that as we get into January, we are going to see an increase in the momentum, which, Jim, I hope allows us to catch up to the projected pace."

Michael Pratt, a spokesman for Operation Warp Speed, reiterated that the number of doses administered reported by the CDC is likely an undercount due to data reporting delays.

"Operation Warp Speed remains on track to have approximately 40 million doses of vaccine and allocate 20 million doses for first vaccinations by the end of December 2020, with distribution of the 20 million first doses spanning into the first week of January as states place orders for them," he said in a statement.

Dr. Atul Gawande, a member of Biden's Covid-19 advisory team, said Tuesday on "CBS This Morning" that the incoming administration does not "have all of the information that's required to understand where the bottlenecks are."

He also noted that he's concerned the Trump administration is being overly optimistic when it comes to the vaccination timeline. Trump's HHS secretary, Alex Azar, has said that the general public should be able to get vaccinated by March.

"I'm worried about over-promising on when things are going to be able to be back to normal," said Gawande, a surgeon at Brigham and Women's Hospital in Boston and a Harvard University professor.

He vowed that the Biden administration will be more transparent about where the problems are, whether it's in manufacturing, distribution or administration of the shots.