The government's top infectious-disease expert Anthony Fauci said Friday that he "absolutely" will accept the offer from President-elect Joe Biden to serve as his chief medical adviser, telling NBC's "Today" that he said yes "right on the spot."

Biden's decision to praise and hire Fauci not only continues the contrast he is trying to create with President Trump, who has talked about firing the doctor, but also shows the calibrated media exposure the president-elect and his team are using to control their message and instill public calm.

Biden said in an interview with CNN's Jake Tapper on Thursday night that on Inauguration Day he will ask Americans to wear a mask for 100 days, "not forever," as a patriotic duty to help curb the spread of the virus until a vaccine is widely available.

Fauci said that he spoke to Biden about that suggestion and told him it was a good idea, but clarified that mask-wearing may still be needed after the 100 days.

On the vaccine front, Fauci told NBC: "As we get into January and February and March, more and more people will be able to get vaccinated. So now is the time to hang in there and not give up."