Biden has arrived at The Queen Theater in Wilmington, Delaware, where he'll receive a briefing on the pandemic from his COVID-19 task force before delivering remarks in which he's expected to take aim at the Trump administration on vaccine distribution.

Ahead of the briefing, the nation's top expert on infectious diseases and Biden's chief medical adviser of COVID-19, Dr. Anthony Fauci, characterized the pandemic as "out of control" and vaccine efforts as falling short.

“We certainly are not at the numbers that we wanted to be at the end of December," Fauci told CNN Tuesday. "You heard taking about 40 million doses for 20 million people. I mean even if you undercount -- two million is an undercount -- how much undercount can there be?”

“Not being responsible myself for the rollout, I can't personally guarantee that we’re gonna catch up," Fauci added later. "I hope we do.”

-ABC News Brian Hartman

Vice President-elect Kamala Harris publicly received her first dose of the Moderna COVID-19 vaccine on Tuesday morning at United Medical Center in Southeast D.C., a predominantly African American community that has been hard hit by the coronavirus pandemic, with Harris telling the public, "this is about saving lives."

"There is a big difference between the vaccines and vaccinations," Harris said after getting the shot, a frequent saying from the president-elect who is expected to take aim at the Trump administration in afternoon remarks on the pace of vaccinations.

"I trust the scientists, and it is the scientists who created and approved this vaccine. So I urge everyone, when it is your turn, get vaccinated. It’s about saving your life, the life of your family members and the life of your community," Harris added.

Asked to respond to the chances of Senate Majority Leader Mitch McConnell bringing the House-passed measure to raise stimulus checks to $2,000 to a vote, Harris promoted her own legislation that's been sitting in the Senate.

"Well, I actually have a bill for that," Harris said with a smile. "Awhile back, I recommended that folks receive a $2,000 check. And so, I would urge Mitch McConnell  to put my bill on the floor for a vote."

Harris' husband, Doug Emhoff, is also receiving the first dose of the Moderna vaccine on Tuesday. Biden and his wife, Jill Biden, publicly received their first doses of the Pfizer vaccine last week. Vice President Mike Pence and the nation's top expert on infectious diseases, Dr. Anthony Fauci, were also vaccinated on camera -- but the Biden transition team is arguing not enough Americans are seeing the same treatment.

More than 2 million Americans have gotten the first doses of a coronavirus vaccine, though officials from Operation Warp Speed said they planned to have 20 million doses of the vaccine distributed to the public by Friday.

-ABC News' Beatrice Peterson, Sarah Kolinovsky and Molly Nagle

Following a briefing with his COVID-19 advisory team on Tuesday, Biden is expected to continue his criticism of the Trump administration in afternoon remarks on the coronavirus pandemic from Wilmington, Delaware, and home in on what his team has characterized as the lagging pace of vaccine distribution.

According to a transition official, Biden will provide an update on the current state of the pandemic and give a dire prediction that, tragically, infection and death rates will rise in the coming weeks. Biden is also expected to address the current administration falling short on its pace for vaccinations, the official said, as well as his plan to get 100 million vaccinations in 100 days.

Biden on Monday slammed the Trump administration for, he said, leaving security agencies "hollowed out" and for creating "roadblocks" for his transition team seeking access to key national security information -- a comment that acting Defense Secretary Christopher Miller has pushed back on, saying the Biden team has already been given more interviews and documents than they initially requested.

Vice President-elect Kamala Harris and her husband, Doug Emhoff, on Tuesday morning are slated to receive their first doses of the COVID-19 vaccine in Washington, D.C., where Harris may also comment on the incoming administration's vaccine distribution plans.

Trump, meanwhile, continued to contest the election on Twitter Tuesday morning -- with three weeks until Biden's inauguration -- criticizing Republican leadership as "pathetic," saying they "only want the path of least resistance" and "only know how to lose." He also attacked Republican lawmakers over their handling of the defensing funding bill as the Senate is expected to override Trump's presidential veto for the first time in his presidency by the end of the week.

After Trump changed course on Sunday and signed the coronavirus relief and government funding bill to avert a shutdown -- though not in time to prevent unemployment benefits to millions of Americans from lapsing -- the House of Representatives on Monday approved Trump's call to increase the coronavirus relief payments from $600 to $2,000.

But its fate in the Senate is uncertain. Senate Majority Leader McConnell has declined to reveal how he will proceed or even whether he’ll bring the proposal up for a vote. Democrats are seizing the opportunity to force Republicans into a difficult position -- either backing or defying Trump.

-ABC News' Molly Nagle and Ben Gittleson

The House on Monday overwhelmingly voted to override Trump's veto of the must-pass sweeping defense policy bill known as the National Defense Authorization Act.

The final vote was 322-87, receiving the two-thirds majority it required. There were 109 Republicans who voted to override the veto and 20 Democrats voted to sustain it.

The Senate is expected to hold its own veto override vote later this week.

If the Senate also overrides the president's veto, it will be the first time Congress has successfully rejected a presidential veto during Trump's presidency.

Shortly before the vote, GOP Rep. Mac Thornberry of Texas, the ranking member of the House Armed Services Committee, urged his colleagues to vote for “the exact same bill” they did before, emphasizing that “not a comma has changed.”

“I would only ask that as members vote, they put the best interests of the country first,” Thornberry said. “There is no other consideration that should matter."

The bill initially cleared both chambers of Congress with veto-proof majorities earlier this month. Trump then officially vetoed the bill last week because it didn't include a repeal of Section 230, a law that shields internet companies from being liable for what is posted on their websites by them or third parties. The bill also included a provision that would rename military bases named after Confederates, which Trump opposed.

The $740 billion bill includes pay raises for America's soldiers, improvements in body armor for women, coronavirus relief, military housing improvements and boosted sexual harassment prevention and response measures, among other items. It has passed both chambers of Congress for 59 years straight with strong bipartisan support.

Some Republicans voted to sustain Trump’s veto despite supporting the bill earlier this month.

The defense bill must become law before noon Jan. 3, when the new session of Congress begins, or it will expire.

-ABC News' Mariam Khan