The headquarters of the National Labor Relations Board (NLRB) is seen in Washington, D.C., U.S., May 15, 2021. REUTERS/Andrew Kelly

The headquarters of the National Labor Relations Board (NLRB) is seen in Washington, D.C., U.S., May 15, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

The seal of the National Labor Relations Board (NLRB) is seen at their headquarters in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

The seal of the National Labor Relations Board (NLRB) is seen at their headquarters in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

The seal of the National Labor Relations Board (NLRB) is seen on books at their headquarters in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

The seal of the National Labor Relations Board (NLRB) is seen at their headquarters in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

The seal of the National Labor Relations Board (NLRB) is seen on books at their headquarters in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

Lauren McFerran, chairman of the National Labor Relations Board (NLRB), poses for a photo in Washington, D.C., U.S., May 14, 2021. REUTERS/Andrew Kelly

A person walks by the Department of Labor headquarters in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

The Department of Labor headquarters is seen in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

The Department of Labor headquarters is seen in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

U.S. Labor Secretary Marty Walsh speaks as Vice President Kamala Harris, Transport Secretary Pete Buttigieg and Director of the White House Office of Public Engagement Cedric Richmond look on at the first meeting of the White House Task Force on Worker Organizing and Empowerment, in the Eisenhower Executive Office Building on the White House campus in Washington, U.S. May 13, 2021. REUTERS/Jonathan Ernst

U.S. Labor Secretary Marty Walsh gestures while speaking to Vice President Kamala Harris, Transport Secretary Pete Buttigieg and Director of the White House Office of Public Engagement Cedric Richmond at the first meeting of the White House Task Force on Worker Organizing and Empowerment, in the Eisenhower Executive Office Building on the White House campus in Washington, U.S. May 13, 2021. REUTERS/Jonathan Ernst

White House labor advisor Seth Harris, U.S. Energy Secretary Jennifer Granholm, Labor Secretary Marty Walsh, and Transport Secretary Pete Buttigieg look on as Vice President Kamala Harris speaks as she opens the first meeting of the White House Task Force on Worker Organizing and Empowerment, from her offices in the Eisenhower Executive Office Building on the White House campus in Washington, U.S. May 13, 2021. REUTERS/Jonathan Ernst

U.S. Vice President Kamala Harris, with Labor Secretary Marty Walsh, opens the first meeting of the White House Task Force on Worker Organizing and Empowerment, from her offices in the Eisenhower Executive Office Building on the White House campus in Washington, U.S. May 13, 2021. REUTERS/Jonathan Ernst

The signage of the Communications Workers of America (CWA) labor union is seen in their headquarters in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

The signage of the Communications Workers of America (CWA) labor union is seen in their headquarters in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

The signage of the Communications Workers of America (CWA) labor union is seen in their headquarters in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

The signage of the Communications Workers of America (CWA) labor union is seen in their headquarters in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

A person walks by the offices of the International Brotherhood of Electrical Workers (IBEW) labor union in Washington, D.C., U.S., May 13, 2021. REUTERS/Andrew Kelly

Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration answers a question during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

U.S. Senator Chris Murphy (D-CT) asks questions during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Rochelle Walensky, Director of the US Centers for Disease Control and Prevention (CDC), testifies before a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Jim Lo Scalzo/Pool via REUTERS

Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health (NIH), testifies before a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Jim Lo Scalzo/Pool via REUTERS

Republican Senator from Louisiana Bill Cassidy questions Rochelle Walensky (not pictured), Director of the US Centers for Disease Control and Prevention (CDC), during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Jim Lo Scalzo/Pool via REUTERS

Sen. Bill Cassidy (R-LA) raises concerns about current COVID-19 guidelines during his questioning at a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, listens to Sen. Rand Paul (R-KY) question him about gain of function research during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Sen. Bill Cassidy (R-LA) raises concerns about current COVID-19 guidelines during his questioning at a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Sen. Susan Collins (R-ME) questions Centers for Disease Control and Prevention Director Dr. Rochelle Walensky during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Centers for Disease Control and Prevention Director Dr. Rochelle Walensky is seen during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Centers for Disease Control and Prevention Director Dr. Rochelle Walensky is seen during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Sen. Rand Paul (R-KY) questions Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, about gain of function research during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration gives an opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, is seen prior to a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Department of Health and Human Services Chief Science Officer for Covid Response David Kessler gives an opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, is seen prior to a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Republican Senator from Kentucky Rand Paul questions Dr. Anthony Fauci (not pictured), Director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health (NIH), during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Jim Lo Scalzo/Pool via REUTERS

Peter Marks, Director of the Center for Biologics Evaluation and Research at the US Food and Drug Administration (FDA), speaks with and Rochelle Walensky, Director of the US Centers for Disease Control and Prevention (CDC), prior to testifying before a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Jim Lo Scalzo/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks to Department of Health and Human Services Chief Science Officer for Covid Response David Kessler before aSenate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Rochelle Walensky, Director of the US Centers for Disease Control and Prevention (CDC), prepares to testify before a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Jim Lo Scalzo/Pool via REUTERS

U.S. Sen. Richard Burr (R-N.C.) makes an opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

U.S. Sen. Rand Paul (R-KY) listens to Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, is seen during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Centers for Disease Control and Prevention Director Dr. Rochelle Walensky gives her opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, gives an opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, gives an opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, gives an opening statement during a Senate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS

Centers for Disease Control and Prevention Director Dr. Rochelle Walensky speaks to Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration before aSenate Health, Education, Labor and Pensions Committee hearing to discuss the on-going federal response to COVID-19, at the U.S. Capitol in Washington, D.C., U.S., May 11, 2021. Greg Nash/Pool via REUTERS