Anthony Fauci had Donald Trump's undivided attention -– or appeared to. He even did something one rarely sees: He touched the president's arm to keep his attention about a potential coronavirus vaccine.

The fascinating exchange came one day after Mr Fauci, head of the National Institute of Allergy and Infectious Diseases, broke into a Cabinet Room session observed by reporters between Mr Trump and pharmaceutical executives. They were there to talk about a possible vaccine to shield people from the virus, which has killed thousands of people around the globe and nine in the United States.

Mr Trump on Monday kept latching on to the industry bigwig's forecasts of moving potential vaccines down the long and winding road of clinical trials in the next three or four months.

It fell to Mr Fauci to make sure the president knew – or to try his best – that the drug makers were talking process, not final outcomes.

"So you're talking over the next few months, you think you could have a vaccine," Mr Trump asked an industry executive on Monday.

Confusing matters, Stephane Bancel, chief executive of Moderna, shot back: "Correct. Correct. With phase two."

Mr Fauci, sensing the president was misleading himself, quickly chimed in.

"Yeah. You won't have a vaccine," he explained to Mr Trump, a sometimes-science skeptic. "You'll have a vaccine to go into testing."

As the back-and-forth with the executives went on, the president kept clinging to his hope that a vaccine could be ready in, as he said at one point, "a couple of months."

That's when Health and Human Services Secretary Alex Azar broke in and said: "It's not a completed vaccine." He meant after the first phase of testing.

Mr Fauci, appearing to sense he and Mr Azar might not have gotten through to the president, tried to explain again on Tuesday when Mr Trump visited the National Institutes of Health near Washington, DC.

The senior public health official clearly had briefed Mr Trump before. Multiple accounts from inside the Oval Office from former aides say the president prefers charts to thick briefing books. So Mr Fauci showed him a series of coronavirus-themed charts on a screen positioned directly in front of Mr Trump.

One explained how vaccine development actually works. Mr Trump looked towards the screen and nodded for several minutes as his subordinate spoke.

At one point, in a remarkable scene, Mr Fauci touched Mr Trump's right arm before saying: "Remember, that doesn't mean you have the vaccine."

He had just walked the former reality television host and New York real estate executive through an explanation of the phases of testing, focusing on phase one.

That's where possible coronavirus vaccines stand now: In the early days and weeks of testing.

As they told Mr Trump on Monday, deploying a fully vetted drug to prevent contraction of the virus likely will take a full calendar year – or possibly more.

Mr Fauci told the president that the chart merely showed "the fastest that you go from the time you get a pathogen, and know what it is, until you do a phase one trial for safety."

Fauci has served in government for decades, under Republican and Democratic presidents.

The coronavirus has again shoved him into the public spotlight, just the kind of career civil servant that Mr Trump and his inner circle despise.

Just last week, Mr Trump's acting White House chief of staff, Mick Mulvaney, said a second term priority would be to clean out the so-called "deep state" because it is not "fair" to the current president that some government employees allegedly worker "harder" for former President Barack Obama.

Yet, Mr Fauci seems to have Mr Trump's attention and trust.

"If Tony is involved, it'll be tomorrow morning. Right, Tony?" Mr Trump asked of one counter-virus measure being considered.