Moderator Susan Page posed the first question to Harris, revealing the first of nine topics: The coronavirus pandemic.

Noting the president's recent diagnosis, Page asked Harris, "What would a Biden administration do in January and February that a Trump administration wouldn't do?"

True to her form as a prosecutor, Harris -- the first Black woman and first Indian American to take a vice presidential debate stage -- laid out her facts, arguing the administration knew about the threat of the virus in January but didn't act soon enough.

"They were informed that it's lethal in consequence, that it's airborne, that it will affect young people," Harris said. "They knew what was happening and they didn't tell you."

Harris then said the Trump administration still doesn't have a plan.

"Well, Joe Biden does and our plan is about what we need to do around a national strategy for contact tracing, for testing, for administration of the vaccine, and making sure that it will be free for all," she said.

There was no handshake between candidates -- customary at the top of such events -- due to COVID-19 precautions. The audience, limited to under 100 attendees, applauded Pence and Harris as they took the stage.

Former Democratic 2020 presidential candidate Pete Buttigieg, who played Pence at some mock debate rehearsals for Harris, was also spotted in the audience.

Pence and Harris have taken the stage in Salt Lake City for the vice presidential debate. The candidates skipped the traditional handshake due to COVID-19 and are divided by plexiglass.

Harris' chief of staff Karine Jean-Pierre told ABC News Chief Anchor George Stephanopoulos that Harris won't spend the night fact-checking Pence on stage.

Instead, the former prosecutor will "bring the case forward" on how Biden and Harris could lead to a different America.

"This debate is about Donald Trump's failure to contain COVID-19, and not just that but to also help working families," said Jean-Pierre, adding Harris has a "very diverse team" that has prepared her for the debate.

Jean-Pierre also criticized the example Trump has set since testing positive for the novel coronavirus last week.

"You have a president right now when he left the White House, he decided that he was going to make a campaign by removing his mask. His rhetoric has been incredibly dangerous," she said. "As Joe Biden said, it's a tragedy that he believes that he was blessed to have this virus, when people are suffering."

Marc Short, Pence's chief of staff, noted that Harris, like Pence, is "also a very skilled debater and has a record as a prosecutor, so I think it will be a very engaging conversation for the American people and hopefully one that shows a clear contrast in visions between the two campaigns."

Short said Pence will argue the case that the Trump administration protected more American lives in its COVID-19 response.

With less than a month to go until the election, early voting has already begun in 33 states and at least 5.5 million votes have been cast -- hitting record numbers across the nation.

According to the United States Elections Project, spearheaded by the University of Florida's political expert, Michael McDonald, an unprecedented 5,618,155 voters have already voted and at least 69,786,179 ballots have been requested in early voting states.

The coronavirus pandemic plays a factor in explaining the large early voting numbers as well as an increase in voter interest. Voters in 2020 are more eager to cast a ballot ahead of Election Day where polling sites could be viewed as overcrowded during pandemic standards.

Seven states --- California, Colorado, Hawaii, Nevada, Oregon, Utah and Washington -- have an all-mail ballot election meaning anyone registered to vote automatically receives a ballot to their registered address.

-ABC News' Kelsey Walsh

HARRIS' CLAIM: "Joe Biden has been so incredibly transparent, and certainly by contrast, the president has not. Both in terms of health records, but also let's look at taxes. We now know because of great investigative journalism that Donald Trump paid $750 in taxes. When I first heard about it, I literally said, you mean $750,000? And it was like, no, $750. We now know Donald Trump owes and is in debt for $400 million."

PENCE'S CLAIM: "The president said those public reports are not accurate and the president's also released literally stacks of financial disclosures the American people can review just as the law allows."

FACT CHECK: As a presidential candidate in 2016 and as a sitting president since, Donald Trump has released annual financial disclosure reports filed to the Federal Election Commission and the Office of Government Ethics, as required by federal laws. Trump's annual personal financial records, which are nearly 100-pages each, show his source of income, other assets, as well as liabilities.

Trump, however, has not released his personal tax records, which is not required by law but has been a decades-long tradition that has been followed by his predecessors in the White House.

Biden and Harris have differentiated themselves from Trump by releasing their federal and state tax returns -- most recently just last week, showing Biden and his wife paid roughly $290,000 in taxes to the federal government in 2019, and Harris and her husband paid about $1.2 million in federal and state taxes last year.

Harris' claim that Trump paid just $750 in taxes comes from The New York Times' recent report. According to the Times, Trump's tax records show that he paid just $750 in federal income taxes the year he ran for president and his first year in the White House.

The report also stated that Trump is personally responsible for loans and other debts totaling $421 million, "with most of it coming due within four years."

--ABC News' Soorin Kim