Bill Gates discloses in newly revealed footage that President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE twice asked him to clarify the difference between HIV and human papillomavirus (HPV).

MSNBC’s “All in With Chris Hayes” aired footage Thursday night of the Microsoft founder speaking at a Gates Foundation event, telling the crowd about two meetings he had with Trump, one at Trump Tower during the presidential transition and another at the White House last year.

“Both times he wanted to know if there was a difference between HPV and HIV,” Gates said. “So I was able to explain that those were rarely confused with each other.”

Exclusive footage obtained by All In... Bill Gates dishes on his meetings with Donald Trump. More tonight at 8PM ET. #inners pic.twitter.com/Zoehj1WTfk — All In w/Chris Hayes (@allinwithchris) May 17, 2018

Coming up: More exclusive footage of Bill Gates talking about avoiding the president, bizarre questions about vaccines, and Trump-style stunts. #inners pic.twitter.com/Z40RgqFvCq — All In w/Chris Hayes (@allinwithchris) May 18, 2018

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Gates also said that at both meetings Trump had asked him about the negative effects of vaccines.

“In both of those two meetings, he asked me if vaccines weren’t a bad thing, because he was considering a commission to look into the ill effects of vaccines,” Gates said.

“And I said, ‘No, that’s a dead end. That would be a bad thing, don’t do that.’”

Gates said last month that Trump was "super interested" in the idea of a universal flu vaccine.

He added that Trump had asked him to be a science adviser, but that he told the president that he didn't believe the role would be a good use of his time.