Women wearing a mask as a measure to prevent contracting the coronavirus disease (COVID-19) walk under an umbrella as it snows in Seoul, South Korea, January 18, 2021. REUTERS/Kim Hong-Ji

People wearing protective face masks apply social distancing as they wait to enter a shop on the first day of the re-opening of retail stores, amid the coronavirus disease (COVID-19) pandemic, in Athens, Greece, January 18, 2021. REUTERS/Alkis Konstantinidis

A woman wearing a protective face mask waits to enter a shop on the first day of the re-opening of retail stores, amid the coronavirus disease (COVID-19) pandemic, in Athens, Greece, January 18, 2021. REUTERS/Alkis Konstantinidis

An Ugandan police APC (Armoured Personnel Carrier) is parked on a soccer field in Kampala, Uganda January 18, 2021. REUTERS/Baz Ratner

Ugandan police APC's (Armoured Personnel Carriers) are parked on a soccer field in Kampala, Uganda January 18, 2021. REUTERS/Baz Ratner

A vial of the Moderna coronavirus disease (COVID-19) vaccine is held at the Misericordia hospital in Grosseto, Italy, January 18, 2021. REUTERS/Jennifer Lorenzini

European Commission President Ursula Von Der Leyen removes her protective face mask as she meets Moldova's President Maia Sandu at the European Commission in Brussels, Belgium, January 18, 2021. REUTERS/Johanna Geron/Pool

European Commission President Ursula Von Der Leyen and Moldova's President Maia Sandu wear protective face masks as they meet at the European Commission in Brussels, Belgium, January 18, 2021. REUTERS/Johanna Geron/Pool

A volunteer who assists medical workers receives a dose of the Moderna coronavirus disease (COVID-19) vaccine at the Misericordia hospital in Grosseto, Italy, January 18, 2021. REUTERS/Jennifer Lorenzini

Ugandan soldiers patrol near the house of Ugandan opposition presidential candidate Robert Kyagulanyi, also known as Bobi Wine in Kampala, Uganda January 18, 2021. REUTERS/Baz Ratner

A volunteer who assists medical workers receives a dose of the Moderna coronavirus disease (COVID-19) vaccine at the Misericordia hospital in Grosseto, Italy, January 18, 2021. REUTERS/Jennifer Lorenzini

European Commission President Ursula Von Der Leyen and Moldova's President Maia Sandu wear protective face masks as they meet at the European Commission in Brussels, Belgium, January 18, 2021. REUTERS/Johanna Geron/Pool

Ugandan soldiers patrol near the house of Ugandan opposition presidential candidate Robert Kyagulanyi, also known as Bobi Wine in Kampala, Uganda January 18, 2021. REUTERS/Baz Ratner

Houthi supporters hold their weapons during a demonstration outside the U.S. embassy against the United States over its decision to designate the Houthis a foreign terrorist organisation, in Sanaa, Yemen January 18, 2021. REUTERS/Khaled Abdullah

European Commission President Ursula Von Der Leyen and Moldova's President Maia Sandu pose as they meet at the European Commission in Brussels, Belgium, January 18, 2021. REUTERS/Johanna Geron/Pool

Indonesian navy personnel carry a body bag during a search and rescue operation for Sriwijaya Air flight SJ 182, which crashed into the Java sea, at Tanjung Priok port in Jakarta, Indonesia, January 18, 2021. REUTERS/Ajeng Dinar Ulfiana

Indonesian navy personnel stand near the debris from the Sriwijaya Air flight SJ 182, which crashed into the Java sea, during a search and rescue operation at Tanjung Priok port in Jakarta, Indonesia, January 18, 2021. REUTERS/Ajeng Dinar Ulfiana

Cypriot President Nicos Anastasiades receives the second dose of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

A student sits in a classroom, as part of the students are allowed to return at the Isacco Newton Scientific College for the first time in months after studying virtually due to the coronavirus disease (COVID-19) restrictions, in Rome, Italy, January 18, 2021. REUTERS/Yara Nardi

A teacher sits in a classroom, as part of the students are allowed to return at the Isacco Newton Scientific College for the first time in months after studying virtually due to the coronavirus disease (COVID-19) restrictions, in Rome, Italy, January 18, 2021. REUTERS/Yara Nardi

Greek Prime Minister Kyriakos Mitsotakis receives the second dose of a vaccine against the coronavirus disease (COVID-19) as Health Ministry representative professor Sotiris Tsiodras stands next to him, at Attikon hospital, in Athens, Greece, January 18, 2021. Yannis Kolesidis/Pool via REUTERS

Greek Prime Minister Kyriakos Mitsotakis greets a man after receiving the second dose of a vaccine against the coronavirus disease (COVID-19) at Attikon hospital, in Athens, Greece, January 18, 2021. Yannis Kolesidis/Pool via REUTERS

A healthcare worker receives a dose of COVISHIELD, a COVID-19 vaccine manufactured by Serum Institute of India, at a government-run hospital at Baruipur on the outskirts of Kolkata, India, January 18, 2021. REUTERS/Rupak De Chowdhuri

Greek Prime Minister Kyriakos Mitsotakis receives the second dose of a vaccine against the coronavirus disease (COVID-19) at Attikon hospital, in Athens, Greece, January 18, 2021. Yannis Kolesidis/Pool via REUTERS

A student stands next to a teacher, as part of the students are allowed to return at the Isacco Newton Scientific College for the first time in months after studying virtually due to the coronavirus disease (COVID-19) restrictions, in Rome, Italy, January 18, 2021. REUTERS/Yara Nardi

Houthi supporters hold their weapons during a demonstration outside the U.S. embassy against the United States over its decision to designate the Houthis a foreign terrorist organisation, in Sanaa, Yemen January 18, 2021. REUTERS/Khaled Abdullah

A sign pointing to a testing centre is seen, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

A man wears personal protective equipment (PPE) at the arrivals area, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

German Health Minister Jens Spahn holds a FPP2 face mask as he addresses the media during a news conference, amid the spread of coronavirus disease (COVID-19), in Berlin, Germany,January 18, 2021. REUTERS/Fabrizio Bensch

German Health Minister Jens Spahn addresses the media during a news conference, amid the spread of coronavirus disease (COVID-19), in Berlin, Germany,January 18, 2021. REUTERS/Fabrizio Bensch

Houthi supporters demonstrate outside the U.S. embassy against the United States over its decision to designate the Houthis a foreign terrorist organisation, in Sanaa, Yemen January 18, 2021. REUTERS/Khaled Abdullah

German Health Minister Jens Spahn holds a FPP2 face mask as he addresses the media during a news conference, amid the spread of coronavirus disease (COVID-19), in Berlin, Germany,January 18, 2021. REUTERS/Fabrizio Bensch

A visitor sits in the Church of the Nativity in the Palestinian town of Bethlehem in the Israeli-occupied West Bank, January 18, 2021. REUTERS/Mussa Qawasma

Cypriot President Nicos Anastasiades receives the second dose of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

An elderly woman receives a vaccine against the coronavirus disease (COVID-19) at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

An elderly woman receives a vaccine against the coronavirus disease (COVID-19) at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

A visitor walks at the Church of the Nativity as the Armenian Patriarch of Jerusalem Nourhan Manougian arrives to celebrate Christmas, in Bethlehem, January 18, 2021. REUTERS/Mussa Qawasma

A man opens the door of a testing center, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

Travellers walk through the arrivals area, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

A labourer covers himself with shawl to avoid cold weather as he sits on a bench at a makeshift cafe amid the coronavirus disease (COVID-19) outbreak in Karachi, Pakistan January 18, 2021. REUTERS/Akhtar Soomro

German Health Minister Jens Spahn addresses the media during a news conference, amid the spread of coronavirus disease (COVID-19), in Berlin, Germany,January 18, 2021. REUTERS/Fabrizio Bensch

A labourer carries a bunch of plastic balls to supply nearby shops along a market as the outbreak of the coronavirus disease (COVID-19) continues in Karachi, Pakistan January 18, 2021. REUTERS/Akhtar Soomro

Worshippers walk as the Armenian Patriarch of Jerusalem Nourhan Manougian(not seen) arrives at the Church of the Nativity to celebrate Christmas, in Bethlehem, January 18, 2021. REUTERS/Mussa Qawasma

A Houthi supporter reacts as he shatters the U.S. flag during a demonstration outside the U.S. embassy against the United States over its decision to designate the Houthis a foreign terrorist organisation, in Sanaa, Yemen January 18, 2021. REUTERS/Khaled Abdullah

Graphic shows Australian Open players who were asked to quarantine for two weeks after passengers on their chartered flight to Melbourne tested positive for COVID-19

People wait outside a testing center, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

Cypriot President Nicos Anastasiades receives the second dose of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

An elderly man receives a vaccine against the coronavirus disease (COVID-19) at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

An elderly man receives a vaccine against the coronavirus disease (COVID-19) at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

A worshipper holding a cross enters the Church of the Nativity as the Armenian Patriarch of Jerusalem Nourhan Manougian arrives to celebrate Christmas, in Bethlehem, January 18, 2021. REUTERS/Mussa Qawasma

A student wearing a protective face mask washes her hands, as schools reopen in Nigeria amid the coronavirus-disease (COVID-19) outbreak, in Abuja, Nigeria January 18, 2021. REUTERS/Afolabi Sotunde

Travellers walk through the arrivals area, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

Houthi supporters hold up their weapons during a demonstration outside the U.S. embassy against the United States over its decision to designate the Houthis a foreign terrorist organisation, in Sanaa, Yemen January 18, 2021. REUTERS/Khaled Abdullah

A nurse speaks to an elderly woman who is about to receive a vaccine against the coronavirus disease (COVID-19) at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

A nurse prepares a vaccine against the coronavirus disease (COVID-19) at the health centre of Latsia in the capital Nicosia, Cyprus January 18, 2021. REUTERS/Yiannis Kourtoglou

Students enter the gate of Government Secondary School Garki, as schools reopen in Nigeria amid the coronavirus-disease (COVID-19) outbreak, in Abuja, Nigeria January 18, 2021. REUTERS/Afolabi Sotunde

Armenian Patriarch of Jerusalem Nourhan Manougian arrives at the Church of the Nativity to celebrate Christmas, in Bethlehem, January 18, 2021. REUTERS/Mussa Qawasma

Travellers walk through the arrivals area, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

A man wears personal protective equipment (PPE) at the arrivals area, as tighter rules for international travellers start, at Heathrow Airport, amid the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, January 18, 2021. REUTERS/Henry Nicholls

Students wear protective face masks during a cleanup exercise, as schools reopen in Nigeria amid the coronavirus-disease (COVID-19) outbreak, in Abuja, Nigeria January 18, 2021. REUTERS/Afolabi Sotunde