U.S. President-elect Joe Biden receives his second coronavirus disease (COVID-19) vaccine at the ChristianaCare Christiana Hospital in Newark, Delaware, U.S., January 11, 2021. REUTERS/Tom Brenner

U.S. President-elect Joe Biden receives his second dose of a vaccine against the coronavirus disease (COVID-19) at ChristianaCare Christiana Hospital in Newark, Delaware, U.S., January 11, 2021. REUTERS/Tom Brenner

U.S. President-elect Joe Biden receives his second dose of a vaccine against the coronavirus disease (COVID-19) at ChristianaCare Christiana Hospital in Newark, Delaware, U.S., January 11, 2021. REUTERS/Tom Brenner

U.S. President-elect Joe Biden receives his second coronavirus disease (COVID-19) vaccine at the ChristianaCare Christiana Hospital in Newark, Delaware, U.S., January 11, 2021. REUTERS/Tom Brenner

U.S. President-elect Joe Biden receives his second dose of a vaccine against the coronavirus disease (COVID-19) at ChristianaCare Christiana Hospital in Newark, Delaware, U.S., January 11, 2021. REUTERS/Tom Brenner