U.S. President Donald Trump twice asked Bill Gates the difference between HIV and HPV, the billionaire philanthropist said at a recent Bill & Melinda Gates Foundation meeting.

In a video aired Thursday by MSNBC's "All In with Chris Hayes," Gates said: "Both times he wanted to know if there was a difference between HIV and HPV, so I was able to explain that those are rarely confused with each other."

According to the Microsoft founder, Trump's questions came after a lengthy discussion about whether vaccines could have a negative impact. The U.S. president was asking if vaccines were "a bad thing."

Gates also said it was "kind of scary" how much Trump knew about his daughter's appearance.

"Melinda didn't like that," he said, referring to his wife.

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