President Trump’s public rebuke of a top federal health official who did not parrot White House talking points about a fast-track coronavirus vaccine is the latest example of the president’s effort to enforce an upbeat narrative about the pandemic, even if that does not square with the facts.

Robert Redfield, director of the Centers for Disease Control and Prevention, is the most recent government physician or scientist to run afoul of Trump’s coronavirus message machine. He did so in congressional testimony Wednesday, saying a vaccine greenlighted later this year would probably not be available to most Americans until sometime in 2021 because those most in need would get the first doses. Redfield also rankled Trump by saying face masks are “more guaranteed to protect me against covid than when I take a covid vaccine.”

Trump said Redfield “made a mistake” on both counts, although the CDC director’s projection about the timetable for vaccine approval and distribution mirrored those of other top officials, including Operation Warp Speed chief scientist Moncef Slaoui and Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases.

“It’s just incorrect information,” Trump said, adding that he had called Redfield after his Senate testimony.

With fewer than 50 days before the Nov. 3 election, Trump has keyed on a prospective coronavirus vaccine as a piece of good news that demonstrates his leadership amid a grinding pandemic, with continued job losses, school closures and disruptions to daily life. Trump argues that the worst of the crisis is past and that states should lift remaining restrictions meant to curb the spread of a disease that has killed nearly 200,000 Americans.

But health and science experts say his continued swipes at the government’s own experts are undermining public trust in their guidance — as well as in an eventual vaccine.

“If you want people to have confidence in a national vaccine program, you don’t trash the director of the CDC, especially when he was accurately describing the likely timeline of the program,” said Tom Inglesby, director of the Johns Hopkins Center for Health Security. “This is the time for U.S. government leaders to be on the same page. Instead it’s personal attacks, contradictions and confusion.”

Americans remain deeply pessimistic about the direction of the country and skeptical of Trump’s handling of the pandemic, according to an Associated Press-NORC Center for Public Affairs Research poll released Thursday.

Only 39 percent of respondents approved of Trump’s handling of the crisis, and about 70 percent said the nation is on the wrong track, the AP reported.

After a confusing flurry of statements Wednesday evening from Redfield and the CDC, White House chief of staff Mark Meadows told reporters Thursday morning that Redfield is not closely involved with the multibillion-dollar vaccine development process.

“That timeline is not consistent with what I have had personal interaction with,” Meadows said at the White House.

A vaccine could be ready as soon as next month and could be administered to those at greatest risk, with a goal of 300 million doses ready to go in January, Meadows said.

“We believe that we can get the vast majority of those at risk with a distribution model that would be available at the end of October,” he said, offering an optimistic scenario based on assumptions that clinical trials will bear fruit within weeks and then win quick approval from the Food and Drug Administration. No one knows if a vaccine will be shown effective by October.

The CDC is one of the lead agencies overseeing vaccine distribution, and its officials wrote reports to Congress and a 57-page planning document to states released Wednesday.

The White House also says the massive public-private vaccine development program, known as Operation Warp Speed, is proof of Trump’s sure-footedness in offering Americans a path forward. The White House has assumed an unusual level of control over that process and the way its progress is described, and has cut some federal experts and agencies out of the loop.

Redfield is only the latest of a number of health and science advisers who have clashed with the White House over the pandemic response, including Health and Human Services Secretary Alex Azar, Fauci and White House coronavirus response coordinator Deborah Birx.

During the same briefing Wednesday where Trump said Redfield had gotten it wrong, the president turned to his favored in-house adviser on the pandemic, Stanford Hoover Institution neuroradiologist Scott Atlas, to describe the document to reporters.

Trump in recent weeks has favored Atlas, who joined the White House this summer. Atlas, who has no background in infectious diseases or epidemiology, has echoed Trump in pushing for schools and college sports to resume, falsely said children and young people have nearly zero health risks from contracting the virus, and pressed for protecting the elderly and vulnerable while letting the rest of the country reopen.

Trump meets with Atlas almost every day, far more than any other health official in his administration, and often invites Atlas to attend press briefings. Atlas did not wear a mask as he sat in the press briefing room Wednesday and then took questions at Trump’s request, although he said he had not been involved in preparing the administration’s planning documents for distribution.

YouTube late last week pulled a video featuring Atlas, in a Hoover Institution interview, questioning universal social distancing measures.

Redfield’s remarks at the Senate hearing Wednesday — that a safe and effective vaccine could be approved by federal regulators and be made available in limited doses in November and December — were consistent with what other health and science officials, such as Fauci and Francis Collins of the National Institutes of Health, have said for weeks.

But they were considered more specific and angered the president, according to one administration official who spoke on the condition of anonymity to share sensitive discussions. “He was the first one who said it quite like that,” the official said.

The first doses are intended to be distributed to high-priority groups, including health-care and other essential workers, according to the administration’s vaccine distribution planning documents released Wednesday by the CDC.

The CDC has told states and localities to prepare for distributing those first doses as early as November.

Large numbers of doses, however, aren’t expected to be widely available until later in 2021, according to Fauci and other health officials.

In his testimony, Redfield echoed that sentiment and said doses would not be “fully available to the American public” until later in 2021. “I think we’re probably looking at late second quarter, third quarter 2021.”

Complicating the finger-pointing were Redfield’s comments about masks as he stressed the importance of safety measures.

Hours later, Redfield sought to clarify his remarks in a pair of tweets, because administration officials were concerned that Redfield’s message would undermine efforts to get people vaccinated, the official said.

Redfield’s tweets, sent at 6:41 p.m. Wednesday, explained that in the absence of a covid-19 vaccine, it was important to rely on measures such as mask-wearing, hand-washing and being careful about crowds.

Redfield’s testimony was encouraging to some at the CDC because he sought to communicate what he knows, based on the latest science and evidence, said another administration official who requested anonymity because they were not authorized to speak on the record.

“Those statements about large amounts of vaccine not being available until 2021 — he’s being very honest,” the official said.

In the past, Redfield has been criticized for failing to defend CDC career scientists against political interference that has tarnished trust in the agency. In the past few months, CDC guidance documents on the safe reopening of churches and schools and testing of asymptomatic individuals have been revised under pressure from the White House. And earlier this week, HHS’s top communications official, Michael Caputo, was put on leave and his senior adviser, Paul Alexander, was removed based in part on backlash to their efforts to edit the agency’s weekly science reports on the virus.

Lenny Bernstein and Yasmeen Abutaleb contributed to this report.