Chairwoman Patty Murray, D-Wash., leaves following the end of a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Roger Marshall, R-Kan., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases, Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team, Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration, watch a Senator speak remotely during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tommy Tuberville, R-Ala., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tommy Tuberville, R-Ala., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tommy Tuberville, R-Ala., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Sen. Richard Burr, R-N.C., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Susan Walsh/Pool via REUTERS

Senator Mike Braun, R-IN., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Susan Walsh/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Susan Walsh/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Susan Walsh/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Chairwoman Patty Murray, D-Wash., listens during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tim Kaine, D-Va., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tammy Baldwin, D-Wis., participates remotely during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Maggie Hassan, D-NH., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases listens during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Lisa Murkowski, R-Alaska, speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases, takes off his face mask during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases, gestures as he speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tim Kaine, D-Va., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tim Kaine, D-Va., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tim Kaine, D-Va., listens during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team, listens during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci attends a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team, listens during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Rochelle Walensky, Director for Centers for Disease Control and Prevention, speaks during at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Lisa Murkowski, R-Alaska, speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Rand Paul, R-Ky., speaks during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

A slide is seen on a TV during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

A slide is seen on a TV during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Susan Collins, R-Maine, speaks during at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Rochelle Walensky, Director for Centers for Disease Control and Prevention, speaks during at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Rand Paul, R-Ky., speaks during at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Rochelle Walensky, Director for Centers for Disease Control and Prevention, speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration speaks during at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Tommy Tuberville R-Ala., listens at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Mitt Romney, R-Utah, listens during a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases speaks at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Rand Paul, R-Ky., listens at a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Richard Burr, R-N.C., Ranking Member of the Senate Committee on Health, Education, Labor, and Pensions, greets Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team, before a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Richard Burr, R-N.C., Ranking Member of the Senate Committee on Health, Education, Labor, and Pensions, greets Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration, before a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Senator Richard Burr, R-N.C., Ranking Member of the Senate Committee on Health, Education, Labor, and Pensions, greets Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases, before a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases speaks with Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team, before the start of a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS

Dr. Anthony Fauci, Director at the National Institute Of Allergy and Infectious Diseases, Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration, Dr. Rochelle Walensky, Director for Centers for Disease Control and Prevention, and Dr. David Kessler, Chief Science Officer of the White House COVID-19 Response Team, speak to one another before a U.S. Senate Health, Education, Labor, and Pensions Committee hearing to examine the COVID-19 response, focusing on an update from federal officials, on Capitol Hill in Washington, U.S., March 18, 2021. Anna Moneymaker/Pool via REUTERS