Dr. Anthony Fauci, the nation’s chief infectious disease expert, says there was never a question that he would accept President-elect Joe Biden’s offer to serve as his chief medical officer and adviser on the coronavirus pandemic.

Fauci told NBC’s “Today” show on Friday, “I said yes right on the spot” after Biden asked him to serve during a conversation on Thursday.

As the director of the National Institute of Allergy and Infectious Diseases, Fauci has served several presidents, Republican and Democratic. But during President Donald Trump’s administration, he has been largely sidelined as Trump gave rosy assessments of the virus and insisted it would fade away.

Fauci has urged rigorous mask-wearing and social distancing, practices that have not often been followed at the White House.

On Thursday, Biden said he will ask Americans to commit to 100 days of wearing masks as one of his first acts as president.

“I told him I thought that was a good idea,” Fauci told NBC.