On Sunday, Dr. Anthony Fauci, chief medical adviser to President Joe Biden, echoed a warning that rolling back public health restrictions on mask-wearing and mass gatherings too quickly could lead to a spike in COVID cases as the nation races to vaccinate millions of people each day and a more contagious and potentially dangerous COVID variant spreads throughout the United States. As of Sunday, the United States reported, on average, 60,000 new COVID cases and 2,000 deaths per day.