Journalists and police stand outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Journalists work outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Police officers stand outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

A police officer stands outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Members of the media work outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Members of the media stand outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Police officers stand outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Police officers stand outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Police officers stand outside St Bartholomew's Hospital, where Britain's Prince Philip has been admitted, in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

A medical worker receives a dose of the AstraZeneca vaccine against the coronavirus disease (COVID-19) at a hospital in Lviv, Ukraine, March 1, 2021. REUTERS/Pavlo Palamarchuk

A medical worker fills a syringe with the AstraZeneca vaccine against the coronavirus disease (COVID-19) before administering an injection at a hospital in Lviv, Ukraine, March 1, 2021. REUTERS/Pavlo Palamarchuk

A medical worker fills a syringe with the AstraZeneca vaccine against the coronavirus disease (COVID-19) before administering an injection at a hospital in Lviv, Ukraine, March 1, 2021. REUTERS/Pavlo Palamarchuk

A medical worker receives a dose of the AstraZeneca vaccine against the coronavirus disease (COVID-19) at a hospital in Lviv, Ukraine, March 1, 2021. REUTERS/Pavlo Palamarchuk

Members of the media stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

A TV reporter speaks outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Hospital staff stand next to an ambulance outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

An ambulance leaves King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Hospital staff stand next to an ambulance outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Hospital staff and people holding umbrellas stand next to an ambulance outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

People hold open umbrellas to cover the field of vision of the area where hospital staff was standing next to an ambulance outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Hospital staff stand next to an ambulance outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Hospital staff stand next to an ambulance outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

An ambulance leaves King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Malnourished girl Ahmadiya Juaidi, 13, holds cups of supplemental nutrition shake she received at malnutrition treatment ward of al-Sabeen hospital in Sanaa, Yemen February 24, 2021. Picture taken February 24, 2021. REUTERS/Khaled Abdullah

Malnourished girl Ahmadiya Juaidi, 13, drinks a supplemental nutrition shake at malnutrition treatment ward of al-Sabeen hospital in Sanaa, Yemen February 24, 2021. Picture taken February 24, 2021. REUTERS/Khaled Abdullah

Malnourished girl Ahmadiya Juaidi, 13, waits to receive a supplemental nutrition shake at malnutrition treatment ward of al-Sabeen hospital in Sanaa, Yemen February 24, 2021. Picture taken February 24, 2021. REUTERS/Khaled Abdullah

Police officers stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Police officers are reflected on the lens of a TV camera as they stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Police officers stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, March 1, 2021. REUTERS/Henry Nicholls

Hospital workers join a protest calling for free, safe, and most efficacious coronavirus disease (COVID-19) vaccines from the gates of the Lung Center of the Phillipines where the government kicked off its COVID-19 vaccination campaign with Sinovac Biotech's Coronavac vaccines, at Quezon City, Metro Manila, Philippines, March 1, 2021. REUTERS/Eloisa Lopez

Medical workers wait to receive a vaccine for the coronavirus disease (COVID-19) during a vaccination program at Kuala Lumpur Hospital in Kuala Lumpur, Malaysia March 1, 2021. REUTERS/Lim Huey Teng

A medical worker shows a dose of a vaccine for the coronavirus disease (COVID-19), during a vaccination program at Kuala Lumpur Hospital in Kuala Lumpur, Malaysia March 1, 2021. REUTERS/Lim Huey Teng

A medical worker receives a vaccine for the coronavirus disease (COVID-19) during a vaccination program at Kuala Lumpur Hospital in Kuala Lumpur, Malaysia March 1, 2021. REUTERS/Lim Huey Teng

A medical worker receives a vaccine for the coronavirus disease (COVID-19) during a vaccination program at Kuala Lumpur Hospital in Kuala Lumpur, Malaysia March 1, 2021. REUTERS/Lim Huey Teng

Medical workers wait to receive a vaccine for the coronavirus disease (COVID-19) during a vaccination program at Kuala Lumpur Hospital in Kuala Lumpur, Malaysia March 1, 2021. REUTERS/Lim Huey Teng

A medical worker prepares a dose of a vaccine for the coronavirus disease (COVID-19), during a vaccination program at Kuala Lumpur Hospital in Kuala Lumpur, Malaysia March 1, 2021. REUTERS/Lim Huey Teng

Members of the media stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

Police officers stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

A camera is seen in front of police officers standing outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

Police officers are seen on duty outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

People ride their bicycles next to police officers standing outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

A doorman and police officers are reflected in a window, outside King Edward VII's Hospital where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

A doorman stands outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

Police officers are seen on duty outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

Police officers stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

Police officers stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

A police officer stands outside King Edward VII's Hospital, where Britain's Prince Philip was admitted in London, Britain, February 28, 2021. REUTERS/Peter Cziborra

A medical worker prepares a dose of AstraZeneca's vaccine against the coronavirus disease (COVID-19) at a hospital in Kabul, Afghanistan February 28, 2021. REUTERS/Mohammad Ismail

A hospital worker receives the first dose of AstraZeneca's vaccine against the coronavirus disease (COVID-19) at a hospital in Kabul, Afghanistan February 28, 2021. REUTERS/Mohammad Ismail

A hospital worker receives the first dose of AstraZeneca's vaccine against the coronavirus disease (COVID-19) at a hospital in Kabul, Afghanistan February 28, 2021. REUTERS/Mohammad Ismail

Police officers are seen on duty outside King Edward VII's Hospital, where Britain's Prince Philip was admitted, in London, Britain February 28, 2021. REUTERS/Toby Melville

A police officer is seen through the camera viewfinder as he stands outside King Edward VII's Hospital, where Britain's Prince Philip was admitted, in London, Britain February 28, 2021. REUTERS/Toby Melville

Police officers are seen on camera display as they stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted, in London, Britain February 28, 2021. REUTERS/Toby Melville

Police officers stand outside King Edward VII's Hospital, where Britain's Prince Philip was admitted, in London, Britain February 28, 2021. REUTERS/Toby Melville

A man receives the Sinovac coronavirus disease (COVID-19) vaccine at the Samut Sakhon hospital in Samut Sakhon province, Thailand, February 28, 2021. REUTERS/Athit Perawongmetha

A health worker administers the Sinovac coronavirus disease (COVID-19) vaccine at the Samut Sakhon hospital in Samut Sakhon province, Thailand, February 28, 2021. REUTERS/Athit Perawongmetha

A health worker prepares to administer the Sinovac coronavirus disease (COVID-19) vaccine at the Samut Sakhon hospital in Samut Sakhon province, Thailand, February 28, 2021. REUTERS/Athit Perawongmetha

A health worker prepares to administer the Sinovac coronavirus disease (COVID-19) vaccine at the Samut Sakhon hospital in Samut Sakhon province, Thailand, February 28, 2021. REUTERS/Athit Perawongmetha

A woman receives the Sinovac coronavirus disease (COVID-19) vaccine at the Samut Sakhon hospital in Samut Sakhon province, Thailand, February 28, 2021. REUTERS/Athit Perawongmetha

A woman receives the Sinovac coronavirus disease (COVID-19) vaccine at the Samut Sakhon hospital in Samut Sakhon province, Thailand, February 28, 2021. REUTERS/Athit Perawongmetha