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

Page pivoted the conversation to climate change, noting the U.S. has seen record-setting hurricanes in the South and record-setting wildfires in the West this year, setting the stakes and posing the first question to the vice president.

"Do you believe, as the scientific community has concluded, that man-made climate change has made wildfires hotter and more deadly and hurricanes wetter and more damaging?" Page asked.

Pence didn't directly answer but warned Harris would sign the U.S. back into the Paris Climate Accord and falsely claimed Biden and Harris have committed to abolishing fossil fuel and banning fracking.

"President Trump and I believe that the progress that we have made in a cleaner environment has been happening precisely because we have a strong free market economy," Pence said.

Harris, once a proponent of the Green New Deal as both a co-sponsor of Sen. Bernie Sanders' bill and as a presidential candidate -- is now embracing Biden's climate plan and defended her running mate's record.

"First of all, I will repeat, and the American people know, that Joe Biden will not ban fracking. That is a fact. That is a fact," Harris began. "We have seen a pattern with this administration, which is, they don't believe in science."

"Joe sees what's happening on the Gulf states, which are being battered by storms. Joe has seen and talked with the farmers in Iowa whose entire crops have been destroyed because of floods. And so Joe believes, again, in science," Harris said, adding that a Biden-Harris administration would "re-enter the climate agreement with pride."

Page then asked if Pence agrees with Harris that climate change poses an existential threat to humans.

"As I said, Susan, the climate is changing. We'll follow the science," Pence said, before launching into an attack on Biden's tax plan.