President Trump’s latest broadside against one of his administration’s public health officials has shined a spotlight on his distrust of experts and placed Centers for Disease Control and Prevention (CDC) Director Robert Redfield in a potentially untenable position.

The president on Wednesday contradicted Redfield’s congressional testimony on vaccine distribution and the efficacy of masks, telling reporters he phoned the CDC director to inform him he was mistaken. 

The White House and GOP allies on Thursday piled on.

Trump chief of staff Mark Meadows said Redfield was not among “those closest to the process” of planning for vaccine development and distribution.

“I’m not sure where Dr. Redfield got his particular timetable, but it is not based on those that are closest to the process,” Meadows said on "Fox & Friends."

House Minority Leader Kevin McCarthy (R-Calif.) chimed in that he’d take the word of Trump over Redfield.

The situation is just the most recent instance of Trump undercutting public health professionals and officials in his own administration, and it’s far from the first time Redfield has been put in a compromising situation by the president. 

Redfield drew scrutiny in March when he showered Trump with praise during a visit to the CDC headquarters, and the president inaccurately proclaimed any American who wanted a COVID-19 test could get one.

Then in April, Trump insisted Redfield dispute his comments to The Washington Post that the winter would be especially challenging because of the combination of flu season and COVID-19. The CDC director acknowledged he had been accurately quoted.

Most recently, guidance on who to test for COVID-19 was changed to recommend against the testing of people who had been exposed but were asymptomatic. And just this week, top communications officials in the Department of Health and Human Services came under fire for trying to control the content and timing of the CDC’s weekly scientific reports on the pandemic.

The president said Wednesday he has confidence in Redfield, and officials said it’s unlikely Trump would fire the CDC director in the middle of the pandemic and so close to Election Day.

But public health experts and former CDC officials argued Redfield should more forcefully defend the agency's reputation and the integrity of its work.

“I think that for the integrity of the agency and the integrity of its career scientists, Dr. Redfield should honorably resign,” said Lawrence Gostin, a Georgetown University professor who has worked with the CDC for decades. “Not because he’s done anything wrong, but as a way to stand up against political pressure."

Gostin said he would expect Trump to replace Redfield with a “puppet,” but that the director should draw a line in the sand.

“I’ve never seen the morale of the staff and the agency so low,” Gostin said. “I’ve never seen people so deflated as is the case at the CDC right now. This should be the moment that the CDC shines.”

Redfield's latest dust-up with Trump began Wednesday morning, when he told a Senate panel that wearing a mask could be a more effective tool to guard against the virus than a vaccine, and that an effective COVID-19 vaccine likely would not be widely available to the general public until mid-2021. 

“If you’re asking me, when is it going to be generally available to the American public, so we can begin to take advantage of a vaccine to get back to our regular life? I think we’re probably looking at late second quarter, third quarter 2021,” Redfield said.

His comments on vaccine timing echoed those made by the leader of the administration's Operation Warp Speed project, who wrote last month that the goal is to have 300 million doses “available and deployed by mid-2021.”

But less than 10 hours after Redfield’s testimony, Trump twice contradicted him.

“No, the mask is not as important as the vaccine,” Trump said. “He made a mistake.”

Trump told reporters he called up Redfield to chastise him over his testimony, and once again offered up his own optimistic timeline that a vaccine will be ready before Election Day.

“We’re not looking to say, ‘Gee, in six months, we’re going to start giving it to the general public.’ No, we want to go immediately,” Trump said. “It could be in October, sometime in October or November. I don’t think it’s going to be much later than that.”

After Trump's remarks, Redfield attempted to smooth out his messaging, tweeting: “I 100% believe in the importance of vaccines and the importance in particular of a #COVID19 vaccine. A COVID-19 vaccine is the thing that will get Americans back to normal everyday life.”

But experts said the constant stream of mixed messages coming from the White House and the administration's own public health agencies is eating away at the credibility of both Redfield and the agency he leads.

“I understand that Dr. Redfield is in a difficult position as a political appointee to President Trump and as a public health expert, but we expect for Dr. Redfield to stand up for the career scientists that he represents, to safeguard the integrity of ... the CDC,” said Leana Wen, an emergency physician and public health professor at George Washington University who previously served as Baltimore's health commissioner.  

Mark Rosenberg, who ran the CDC’s National Center for Injury Prevention and Control from 1994 to 1999, said Redfield needs to “walk the walk of a leader of a scientific institution.”

Rosenberg said Redfield shouldn't start criticizing Trump, but he also shouldn't back down under political broadsides.

“He has to be seen as a protector of science, because there are 12,000 people who work tirelessly for CDC ... and Dr. Redfield has to give those people a reason to continue what they're doing,” Rosenberg said. “He can't let the science be changed by the White House.”

Rosenberg said he thinks there are ways Redfield can take a stand without resigning.

“I think the first step before considering resigning would be to try to mount a defense of the truth, and of the institution's reputation ... it's very important not only to get the facts out, but to restore trust in the agency,” Rosenberg said.