WATCH: Joe Biden states that Kamala Harris is the President-elect

"I took it to instill public confidence in the vaccine," Biden said. "President-elect Harris took hers today for the same reason.

"And when the president's doctors recommend it President Trump should take it and instill the same degree of confidence."

President Trump contracted the coronavirus in October and was treated for the illness at Walter Reed Medical Center. After he recovered from it, he offered to donate plasma to help others recover as well.

This isn't the first time that members of the Biden Harris team have been confused about which one of the two is to be the next American president.

At a campaign stop in Fort Worth, Texas on Oct. 30, Kamala Harris was introduced as the "next president of the United States." She was on the ballot as the a candidate for vice president, although people on staff in Fort Worth didn't seem to be aware of that.

"Without further delay, I am so honoured to introduce the next President of the United States Senator Kamala Harris!" Rebecca Acuna announced.

Biden has claimed that he is a "bridge" president, meaning that he intends to bridge the gap between his perceived centrism and the further left-leaning side of the Democrat party.