A member of NHS stuff stands outside of St Bartholomew's Hospital entrance, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Matthew Childs

U.S. Senator Maggie Hassan (D-NH) questions witnesses during a Senate Health, Education, Labor, and Pensions Committee nomination hearing on Capitol Hill in Washington, U.S., February 24, 2021. REUTERS/Tom Brenner/Pool

Sen. Maggie Hassan (D-NH) questions Xavier Becerra, U.S. President Joe Biden's nominee for Secretary of Health and Human Services, during his confirmation hearing before the Senate Health, Education, Labor and Pensions Committee at the U.S. Capitol in Washington, U.S., February 23, 2021. Leigh Vogel/Pool via REUTERS

Sen. Maggie Hassan (D-NH) questions Xavier Becerra, U.S. President Joe Biden's nominee for Secretary of Health and Human Services, during his confirmation hearing before the Senate Health, Education, Labor and Pensions Committee at the U.S. Capitol in Washington, U.S., February 23, 2021. Leigh Vogel/Pool via REUTERS

A member of NHS Test and Trace staff sets up a mobile testing centre amid the outbreak of the coronavirus disease (COVID-19) in the Moston area of Manchester, Britain, February 17, 2021. REUTERS/Phil Noble

A member of NHS Test and Trace staff laughs with a member of the public as they take a test at a mobile testing centre amid the outbreak of the coronavirus disease (COVID-19) in the Moston area of Manchester, Britain, February 17, 2021. REUTERS/Phil Noble

A member of NHS Test and Trace staff sets up a mobile testing centre amid the outbreak of the coronavirus disease (COVID-19) in the Moston area of Manchester, Britain, February 17, 2021. REUTERS/Phil Noble

A member of NHS Test and Trace staff sets up a mobile testing centre amid the outbreak of the coronavirus disease (COVID-19) in the Moston area of Manchester, Britain, February 17, 2021. REUTERS/Phil Noble

A member of NHS Test and Trace staff sets up a mobile testing centre amid the outbreak of the coronavirus disease (COVID-19) in the Moston area of Manchester, Britain, February 17, 2021. REUTERS/Phil Noble

A member of NHS Test and Trace staff talks to a member of the public as they take a test at a mobile testing centre amid the outbreak of the coronavirus disease (COVID-19) in the Moston area of Manchester, Britain, February 17, 2021. REUTERS/Phil Noble

Chief Medical Officer for England Chris Whitty, British Prime Minister Boris Johnson and Chief Executive of NHS in England Simon Stevens attend a coronavirus pandemic media briefing at Downing Street, London, Britain February 15, 2021. Stefan Rousseau/PA Wire/Pool via REUTERS

Senators Kirsten Gillibrand (D-NY), Elizabeth Warren (D-MA) and Maggie Hassan (D-NH) depart after the day's proceedings concluded in the impeachment trial of former U.S. President Donald Trump, on charges of inciting the deadly attack on the U.S. Capitol, on Capitol Hill in Washington, U.S., February 10, 2021. REUTERS/Joshua Roberts/Pool

Dr Nikki Kanani, medical director of primary care for NHS England and NHS improvement, gives an update on the COVID-19 pandemic at a virtual news conference at 10 Downing Street in London, Britain February 8, 2021. Undocumented migrants in Britain will still be able to get COVID vaccines without being subject to status checks, the government said on Monday. Tolga Akmen/Pool via REUTERS

Dr Nikki Kanani, medical director of primary care for NHS England and NHS improvement, gives an update on the COVID-19 pandemic at a virtual news conference at 10 Downing Street in London, Britain February 8, 2021. Undocumented migrants in Britain will still be able to get COVID vaccines without being subject to status checks, the government said on Monday. Tolga Akmen/Pool via REUTERS

A sign supporting NHS workers is seen by the roadside during snowfall, as Storm Darcy affects large parts of the country, in Sevenoaks, Britain, February 8, 2021. REUTERS/Toby Melville

Badges are seen on the chest of NHS worker at the COVID-19 vaccine center at Basingstoke Fire Station, in Basingstoke, Britain February 4, 2021. REUTERS/Peter Cziborra

An NHS sign is displayed at the coronavirus disease (COVID-19) vaccination centre at Cliffs Pavilion in Southend-on-Sea, Britain, February 4, 2021. REUTERS/Paul Childs

A member of the NHS vaccine support staff works at Basingstoke Fire Station, amid the coronavirus disease (COVID-19) outbreak, in Basingstoke, Britain February 4, 2021. Andrew Matthews/Pool via REUTERS

Junior soldiers at the Army Foundation College applaud during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Harrogate, North Yorkshire, Britain February 3, 2021. Peter Byrne/Pool via REUTERS

Junior soldiers at the Army Foundation College applaud during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Harrogate, North Yorkshire, Britain February 3, 2021. Peter Byrne/Pool via REUTERS

Junior soldiers at the Army Foundation College applaud during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Harrogate, North Yorkshire, Britain February 3, 2021. Peter Byrne/Pool via REUTERS

Junior soldiers at the Army Foundation College applaud during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Harrogate, North Yorkshire, Britain February 3, 2021. Peter Byrne/Pool via REUTERS

Scotland's First Minister Nicola Sturgeon applauds outside St Andrews House during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Ediburgh, Scotland, Britain February 3, 2021. Jeff J Mitchell/Pool via REUTERS

Scotland's First Minister Nicola Sturgeon applauds outside St Andrews House during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Ediburgh, Scotland, Britain February 3, 2021. Jeff J Mitchell/Pool via REUTERS

Scotland's First Minister Nicola Sturgeon applauds outside St Andrews House during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Ediburgh, Scotland, Britain February 3, 2021. Jeff J Mitchell/Pool via REUTERS

Scotland's First Minister Nicola Sturgeon applauds outside St Andrews House during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Ediburgh, Scotland, Britain February 3, 2021. Jeff J Mitchell/Pool via REUTERS

Scotland's First Minister Nicola Sturgeon applauds outside St Andrews House during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Ediburgh, Scotland, Britain February 3, 2021. Jeff J Mitchell/Pool via REUTERS

Scotland's First Minister Nicola Sturgeon applauds outside St Andrews House during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Ediburgh, Scotland, Britain February 3, 2021. Jeff J Mitchell/Pool via REUTERS

Residents of Trellick Tower can be seen on their balconies during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak in London, Britain, February 3, 2021. REUTERS/Henry Nicholls

Residents of Trellick Tower can be seen on their balconies during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak in London, Britain, February 3, 2021. REUTERS/Henry Nicholls

Residents of Trellick Tower can be seen on their balconies during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak in London, Britain, February 3, 2021. REUTERS/Henry Nicholls

Britain's Prime Minister Boris Johnson and partner Carrie Symonds applaud outside 10 Downing Street during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in London, Britain, February 3, 2021. REUTERS/John Sibley

A bus displaying a RIP message drives past the house of late Captain Sir Tom Moore during a national clap for him and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Marston Moretaine, near Milton Keynes, Britain February 3, 2021. REUTERS/Andrew Couldridge

Residents participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Twerton, near Bath, Britain February 3, 2021. REUTERS/Andrew Boyers

Hannah Ingram-Moore and her family attend a national clap for late Captain Sir Tom Moore and all NHS workers, at the gate to the residence of late Captain Sir Tom Moore in Marston Moretain, amidst the coronavirus disease (COVID-19) outbreak, near Milton Keynes, Britain February 3, 2021. REUTERS/Hannah McKay

A bus displaying a RIP message drives past the house of late Captain Sir Tom Moore during a national clap for him and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Marston Moretaine, near Milton Keynes, Britain February 3, 2021. REUTERS/Andrew Couldridge

NHS staff participate during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, outside Bedford Hospital, in Bedford, Britain, February 3, 2021. REUTERS/Matthew Childs

NHS staff participate during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, outside Bedford Hospital, in Bedford, Britain, February 3, 2021. REUTERS/Matthew Childs

NHS staff participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, at Chelsea and Westminster Hospital in London, Britain February 3, 2021. REUTERS/Kevin Coombs

Hannah Ingram-Moore and her family attend a national clap for late Captain Sir Tom Moore and all NHS workers, at the gate to the residence of late Captain Sir Tom Moore in Marston Moretaine, amidst the coronavirus disease (COVID-19) outbreak, near Milton Keynes, Britain February 3, 2021. REUTERS/Hannah McKay

Britain's Prime Minister Boris Johnson and partner Carrie Symonds leave 10 Downing Street to attend a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in London, Britain, February 3, 2021. REUTERS/John Sibley

Residents participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Marston Moretaine, near Milton Keynes, Britain February 3, 2021. REUTERS/Andrew Couldridge

Residents participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Marston Moretaine, near Milton Keynes, Britain February 3, 2021. REUTERS/Andrew Couldridge

Hannah Ingram-Moore and her family attend a national clap for late Captain Sir Tom Moore and all NHS workers, at the gate to the residence of late Captain Sir Tom Moore in Marston Moretaine, amidst the coronavirus disease (COVID-19) outbreak, near Milton Keynes, Britain February 3, 2021. REUTERS/Hannah McKay

Britain's Prime Minister Boris Johnson and partner Carrie Symonds applaud outside 10 Downing Street during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in London, Britain, February 3, 2021. REUTERS/John Sibley

NHS staff participate during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, outside Bedford Hospital, in Bedford, Britain, February 3, 2021. REUTERS/Matthew Childs

NHS staff participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, at Chelsea and Westminster Hospital in London, Britain February 3, 2021. REUTERS/Kevin Coombs

Hannah Ingram-Moore and her family attend a national clap for late Captain Sir Tom Moore and all NHS workers, at the gate to the residence of late Captain Sir Tom Moore in Marston Moretaine, amidst the coronavirus disease (COVID-19) outbreak, near Milton Keynes, Britain February 3, 2021. REUTERS/Hannah McKay

NHS staff participate during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, outside Bedford Hospital, in Bedford, Britain, February 3, 2021. REUTERS/Matthew Childs

Britain's Prime Minister Boris Johnson and partner Carrie Symonds (not pictured) applaud outside 10 Downing Street during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in London, Britain, February 3, 2021. REUTERS/John Sibley

Britain's Prime Minister Boris Johnson and partner Carrie Symonds applaud outside 10 Downing Street during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in London, Britain, February 3, 2021. REUTERS/John Sibley

Residents participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Brentford, London, Britain February 3, 2021. REUTERS/Paul Childs TPX IMAGES OF THE DAY

NHS staff participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, at Chelsea and Westminster Hospital in London, Britain February 3, 2021. REUTERS/Kevin Coombs

Hannah Ingram-Moore and her family attend a national clap for late Captain Sir Tom Moore and all NHS workers, at the gate to the residence of late Captain Sir Tom Moore in Marston Moretaine, amidst the coronavirus disease (COVID-19) outbreak, near Milton Keynes, Britain February 3, 2021. REUTERS/Hannah McKay

Residents participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in Brentford, London, Britain February 3, 2021. REUTERS/Paul Childs

Britain's Prime Minister Boris Johnson and partner Carrie Symonds applaud outside 10 Downing Street during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in London, Britain, February 3, 2021. REUTERS/John Sibley

NHS staff participate in a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, at Chelsea and Westminster Hospital in London, Britain February 3, 2021. REUTERS/Kevin Coombs

NHS staff participate during a national clap for late Captain Sir Tom Moore and all NHS workers, amidst the coronavirus disease (COVID-19) outbreak, outside Bedford Hospital, in Bedford, Britain, February 3, 2021. REUTERS/Matthew Childs

Hannah Ingram-Moore and her family attend a national clap for late Captain Sir Tom Moore and all NHS workers, at the gate to the residence of late Captain Sir Tom Moore in Marston Moretaine, amidst the coronavirus disease (COVID-19) outbreak, near Milton Keynes, Britain February 3, 2021. REUTERS/Hannah McKay

Britain's Prime Minister Boris Johnson and partner Carrie Symonds applaud outside 10 Downing Street during a national clap for late Captain Sir Tom Moore and NHS workers, amidst the coronavirus disease (COVID-19) outbreak, in London, Britain, February 3, 2021. REUTERS/John Sibley