During the first open discussion session, Page asked Harris if she would take a COVID-19 vaccine if it was approved by the Trump administration.

"If the public health professionals -- if Dr. Fauci, if the doctors tell us that we should take it, I'll be the first in line to take it, absolutely," Harris said. "But if Donald Trump tells us I should take it -- that we should take it, I'm not taking it."

Page tried to move on to the next topic -- the role of the vice president -- but Pence used his uninterrupted two minutes to respond to Harris' comment on a potential vaccine and to criticize how the Obama administration handled the Swine Flu or H1N1 pandemic of 2009.

"We have five companies in phase three clinical trials and we're right now producing tens of millions of doses," the vice president said.  "So, the fact that you continue to undermine public confidence in a vaccine, if a vaccine emerges during the trump administration, I think is unconscionable."

"And senator, I just ask you, stop playing politics with peoples' lives. The reality is, that we will have a vaccine, we believe, before the end of this year," he added.

In light of the president's recent diagnosis, Page directly asked Pence, "How can you expect Americans to follow the administration's safety guidelines to protect themselves from COVID when you at the White House have not been doing so?"

"Well, the American people have demonstrated over the last eight months that, when given the facts, they're willing to put the health of their families and their neighbors and people they don't know first," Pence said.

Pence also addressed the Sept. 26 Rose Garden event during which social distancing and masks weren't enforced and after which several White House officials tested positive.

"Many of the people who were at that event, Susan, actually were tested for coronavirus, and it was an outdoor event which all of our scientists regularly and routinely advise," Pence said. "The difference here is, President Trump and I trust the American people to make choices in the best interest of their health."

Pence defended the White House's response to the COVID-19 pandemic, saying that Trump "has put the health of America first." Pence pointed to the administration's early ban on travel to China, testing efforts and the efforts to research and administer a vaccine.

Pence also went after the plan the Biden campaign released to combat coronavirus, saying "it reads an awful lot like what President Trump and I, and our task force, have been doing every step of the way."

He said that the plan "looks a little bit like plagiarism," because of its similarity to the White House Coronavirus Task Force plan.

Harris hit back at Pence, citing the revelations that Trump downplayed the coronavirus to prevent panic.

"I want to ask the American people, how calm were you when you were panicked about where you were going to get your next roll of toilet paper, how calm were you when your kids were were sent home from school? How calm were you when your children couldn't see your parents because they were afraid they could kill them?" she said.

Trump's re-election campaign is looking to have the president return the campaign trail early next week, despite his COVID-19 diagnosis last Thursday and hospital stay over the weekend.

The campaign was forced to cancel five previously announced rallies due to the president's testing positive. Multiple sources tell ABC News the Trump team has begun working to nail down details for the president's return to the campaign trail and has considered an event -- possibly in Pennsylvania -- as early as next Monday.

ABC News' Will Steakin, Katherine Faulders and John Santucci

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