No face mask for Vice President Mike Pence as he tours Mayo's COVID-19 testing labs in Rochester

Vice President Mike Pence returned to Minnesota on Tuesday to highlight Mayo Clinic's coronavirus research and testing efforts, calling them a "whole-of-Minnesota approach."

But even as he praised Mayo's efforts to combat COVID-19, Pence ignored the clinic's request that all visitors don face masks to prevent transmission, including Gov. Tim Walz and others on the tour. In the face of growing commentary on television and social media as the tour got underway, Mayo officials responded with a tweet:

"Mayo Clinic had informed @VP of the masking policy prior to his arrival today." The tweet was later deleted without explanation, and Pence told reporters afterward that the precaution wasn't necessary because he is regularly tested.

Pence's visit followed Walz's announced "moon shot" plan to partner with Mayo Clinic and the University of Minnesota to ramp up virus testing in the state. Mayo's national reference laboratory has already conducted 150,000 molecular diagnostic tests for COVID-19 nationwide.

The DFL governor greeted Pence after Air Force Two landed at the Rochester airport shortly before noon. They were joined by the governor's daughter, Hope Linn, and U.S. Rep. Jim Hagedorn, a Republican who represents southern Minnesota.

At the first stop inside Mayo Clinic, Pence talked to Dr. Michael Joyner, who was with Dennis Nelson, a clinic employee who said he had recovered from a "mild" case of COVID-19 and decided to donate plasma for therapy treatment to help other patients with the virus. Pence thanked the employee and elbow-bumped him on his way out.

Dr. Matthew J. Binnicker walked Pence through the Mayo Clinic lab and gave a brief overview of how the clinic developed its diagnostic testing and its partnership with the U to ramp up to testing "anyone who needs one" soon.

"The president and I often talk about a whole-of-America approach; this is a whole-of-Minnesota approach," Pence said after being briefed. Pence said they are "very excited" about the prospect of antibody testing, which tells doctors if a patient has already had the virus and has since recovered.

Pence, leading the Trump administration's Coronavirus Task Force, cited Minnesota's "breakthrough" at a White House briefing last week as an example of state-level progress on testing. The visit follows his trip in March to the 3M Innovation Center in Maplewood, where he described an "all-hands-on-deck effort" to combat the spread of coronavirus.

State health officials on Tuesday acknowledged some startup delays in the rapid expansion of COVID-19 testing and that it was unclear whether they would meet Walz's goal of conducting 5,000 molecular diagnostic tests per day starting May 4 — when Minnesota's statewide stay-at-home order is slated to end.

State Health Commissioner Jan Malcolm said she believes the state is on track within a month to conduct 20,000 diagnostic tests per day, though, as part of a $36 million partnership with Mayo and the University of Minnesota.

Even then, Malcolm said the state would need to be strategic with its testing capacity — and that while the goal is testing for anybody with COVID-19-like symptoms, tests must be available for long-term care residents who are particularly vulnerable, and to respond to hot spots such as the outbreaks in meatpacking plants that happened "quickly and at a scale that we didn't anticipate."

"It's not so much about a specific number but learning what we need to test smartly," Malcolm said.

Of the 301 COVID-19 deaths reported in Minnesota as of Tuesday, 233 involved long-term care residents. The state also reported 365 newly lab-confirmed COVID-19 cases on Tuesday, a single-day record that was partly due to increased testing statewide but also in part to a focus on meatpacking workers. The JBS pork plant in Worthington remained shut down on Tuesday after an outbreak that has now contributed to 477 lab-confirmed cases in Nobles County alone.

Pence's two visits to Minnesota during the coronavirus pandemic have put a national focus on the state's leading-edge medical and biotechnology sectors even as the DFL governor navigates President Donald Trump's fraught relationship with other state governors.

Although Trump encouraged a recent anti-lockdown protest in Minnesota, he has refrained from attacking Walz directly and has praised the state's public health efforts. "We are working closely on getting him all he needs, and fast," Trump tweeted earlier this month. "Good things happening!"

While the visit was intended to reinforce the administration's commitment to fighting the coronavirus, Minnesota Democrats criticized Trump and Pence for what they see as a broadly insufficient federal response to the pandemic, forcing Minnesota to compete against other states and countries for needed medical supplies.

State Rep. Tina Liebling, a DFLer whose district includes the Mayo Clinic campus, said Tuesday that the insufficient federal response is the chief reason for the need to move slowly in lifting stay-at-home orders in Minnesota and elsewhere.

"What we need is a massive, unified production of personal protective equipment," Liebling said. "That would go a long way to opening the economy. President Trump has said, 'Liberate Minnesota.' We say liberate testing, liberate planning and coordination, liberate personal protective equipment."

The campaign of former Vice President Joe Biden put out a statement characterizing the tour as an attempt to "paper over the Trump Administration's delayed, insufficient response to this pandemic by passing the buck to governors and posing for photos at the finish line."

Pence, for his part, sought to minimize the politics of the pandemic. "We will get through this, we will get through this together," he said before a roundtable discussion with Mayo staff broke up.

He also explained his decision to forgo a face mask at the clinic.

"As vice president of the United States, I'm tested for the coronavirus on a regular basis, and everyone who is around me is tested for the coronavirus," he said, noting that federal guidelines indicate that the mask is good for preventing the spread of the virus by those who have it. "And since I don't have the coronavirus, I thought it'd be a good opportunity for me to be here, to be able to speak to these researchers, these incredible health care personnel, and look them in the eye and say thank you."

State health officials on Tuesday also discussed a developing strategy to use thousands of blood serum tests to identify antibodies in patients who have recovered from COVID-19 and to define just how widely the coronavirus has spread in Minnesota.

While there is hope that the presence of antibodies provides at least temporary immunity from reinfection, Dr. Ruth Lynfield, state epidemiologist, said there is no proof yet and that recovered patients will still need to take precautions.

"It may not be the case that it will have lifelong immunity but I am hopeful that there will be immunity for a period of time," she said. "But this is something that we really have to be very careful about."

Staff writer Patrick Condon contributed to this report.