Upon arriving in Michigan for multiple campaign events Sunday morning, Harris responded to White House Chief of Staff Mark Meadows telling CNN that the United States is "not going to control" the virus.
"They are admitting defeat. And I've been saying that, and Joe Biden has been saying that since the beginning. This is the greatest failure of any presidential administration in the history of America," she said.
Harris also cited rising numbers of COVID-19 cases nationally including 83,718 new cases on Sunday after a single-day record of 83,757 on Saturday.
"We are breaking records of the number of people that are contracting a deadly virus, and this administration fails to take personal responsibility in terms of leading the nation through this dangerous, dangerous and deadly mass-casualty event," said Harris. "And that's why they have forfeited their right to a second term in office."
She also criticized Vice President Mike Pence for traveling to North Carolina on Sunday for a rally in the city of Kinston, despite his chief of staff, Marc Short, one of his top political advisers Marty Obst, and three other staffers testing positive for COVID-19.
Harris resumed travel after suspending campaign plans for a weekend earlier this month when her Communications Director Liz Allen and a member of her flight crew tested positive for COVID-19.
Biden and Harris have largely held drive-in rallies, where attendees remain in their cars to maintain social distancing amid the pandemic, while President Donald Trump has continued to hold his large rallies throughout the country.
At an afternoon "Voter Now drive-in rally" in Pontiac, Mich., Harris again cited an excerpt from Pullitzer-winning journalist Bob Woodward's book, Rage, in which he said the president knowingly downplayed the virus despite knowing it was deadly and airborne in January.
"Donald Trump knew about the seriousness of this back on Jan. 28. He knew. He knew that it could kill people. He knew that it could hurt young people. He knew it was airborne and he sat on that information and did not tell the American people," Harris said. "Could you imagine what you might have done if on Jan. 28 you knew what this was going to be?"
Harris also alluded to an upcoming Supreme Court case surrounding the constitutionality of the Affordable Care Act, which Biden helped to implement during his time in the White House alongside President Barack Obama.
She said while Trump has pushed to undo the healthcare law, Biden would seek to expand healthcare, protect people with pre-existing conditions and lower the age of eligibility for Medicare.
The senator from California, who is the first Black woman nominated by a major party to serve as vice president, also praised Biden for "having the courage and the knowledge of America's history to speak the phrase 'black lives matter.'"
While in Michigan, Harris traveled to Detroit for a drive-in church event in the morning and then spoke at a pair of get-out-the-vote events.
Her visit to Michigan, which Trump won in 2016, comes after former President Barack Obama held a rally in Florida in support of Biden and Harris. The former president said the Trump administration ignored plans left behind by members of his own administration with guidance on how to fight a pandemic.
"We literally left this White House a pandemic playbook to show them how to respond before a virus reached our shores," Obama said. "It must be lost, along with the Republican healthcare plan."
Biden is expected to remain in Delaware on Sunday after campaigning in Pennsylvania on Saturday where he painted a bleak picture of the effects of the pandemic-affected months ahead under Trump's leadership.
"It's going to be a dark winter unless we change our ways," Biden said. "Experts tell us we're going to lose nearly another 200,000 lives nationwide in the next several months, all because this president cares more about the stock market than he does you."