Austria's Chancellor Sebastian Kurz attends a news conference on COVID-19 restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Austria's Chancellor Sebastian Kurz attends a news conference on COVID-19 restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Austria's Vice Chancellor Werner Kogler attends a news conference on COVID-19 restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Residents enjoy the sunrise after starting their fast during the holy month of Ramadan at Ramlet al-Baida beach on Tarout Island, Saudi Arabia, April 23, 2021. REUTERS/Hajer Abdulmohsin

Tables and chairs are pictured next to a closed restaurant as the coronavirus disease (COVID-19) lockdown continues in Vienna, Austria April 23, 2021. REUTERS/Leonhard Foeger

Tables and chairs are pictured next to a closed restaurant as the coronavirus disease (COVID-19) lockdown continues in Vienna, Austria April 23, 2021. REUTERS/Leonhard Foeger

Tables and chairs are pictured next to a closed restaurant as the coronavirus disease (COVID-19) lockdown continues in Vienna, Austria April 23, 2021. REUTERS/Leonhard Foeger

French judicial investigating police officers secure the area where an attacker stabbed a female police administrative worker, in Rambouillet, near Paris, France, April 23, 2021. REUTERS/Gonzalo Fuentes

French judicial investigating police officers secure the area where an attacker stabbed a female police administrative worker, in Rambouillet, near Paris, France, April 23, 2021. REUTERS/Gonzalo Fuentes

Stacked chairs and folded tables are pictured next to a closed restaurant as the coronavirus disease (COVID-19) lockdown continues in Vienna, Austria April 23, 2021. REUTERS/Leonhard Foeger

Stacked chairs are pictured next to a closed restaurant as the coronavirus disease (COVID-19) lockdown continues in Vienna, Austria April 23, 2021. REUTERS/Leonhard Foeger

Tennis - ATP 500 - Barcelona Open - Real Club de Tennis Barcelona, Barcelona, Spain - April 23, 2021 Spain’s Rafael Nadal in action during his quarter final match against Great Britain’s Cameron Norrie REUTERS/Albert Gea

Tennis - ATP 500 - Barcelona Open - Real Club de Tennis Barcelona, Barcelona, Spain - April 23, 2021 FC Barcelona president Joan Laporta watches Spain’s Rafael Nadal in action during his quarter final match against Great Britain’s Cameron Norrie REUTERS/Albert Gea

CMO and co-founder of German biotechnology company BioNTech Ozlem Tureci talks during a press conference after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

CMO and co-founder of German biotechnology company BioNTech Ozlem Tureci talks during a press conference after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

CMO and co-founder of German biotechnology company BioNTech Ozlem Tureci talks during a press conference after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

CMO and co-founder of German biotechnology company BioNTech Ozlem Tureci talks during a press conference after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

A SpaceX Falcon 9 rocket, with the Crew Dragon capsule, is launched carrying four astronauts on a NASA commercial crew mission to the International Space Station at Kennedy Space Center in Cape Canaveral, Florida, U.S., April 23, 2021. REUTERS/Thom Baur

Indonesian police officers walk down the stairs of the ship KRI dr. Soeharso-990 at Tanjung Wangi port, as the search continues for the missing KRI Nanggala-402 submarine in Banyuwangi, East Java Province Indonesia, April 23, 2021. REUTERS/Ajeng Dinar Ulfiana

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

A SpaceX Falcon 9 rocket, with the Crew Dragon capsule, is launched carrying four astronauts on a NASA commercial crew mission to the International Space Station at Kennedy Space Center in Cape Canaveral, Florida, U.S., April 23, 2021. REUTERS/Joe Skipper

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

Police officers secure the area where an attacker stabbed a female police administrative worker, in Rambouillet, near Paris, France, April 23, 2021. REUTERS/Gonzalo Fuentes

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

Tennis - ATP 500 - Barcelona Open - Real Club de Tennis Barcelona, Barcelona, Spain - April 23, 2021 Spain’s Rafael Nadal in action during his quarter final match against Great Britain’s Cameron Norrie REUTERS/Albert Gea

Tennis - ATP 500 - Barcelona Open - Real Club de Tennis Barcelona, Barcelona, Spain - April 23, 2021 Spain’s Rafael Nadal in action during his quarter final match against Great Britain’s Cameron Norrie REUTERS/Albert Gea

A SpaceX Falcon 9 rocket, with the Crew Dragon capsule, is launched carrying four astronauts on a NASA commercial crew mission to the International Space Station at Kennedy Space Center in Cape Canaveral, Florida, U.S., April 23, 2021. REUTERS/Joe Skipper

Belgium's Prime Minister Alexander De Croo, Pfizer CEO Albert Bourla, CMO and co-founder of German biotechnology company BioNTech Ozlem Tureci, European Commission President Ursula von der Leyen and Pfizer Manufacturing Belgium's Managing Director Luc Van Steenwinkel pose for a group photograph after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

A police officer stands guard in the area where an attacker stabbed a female police administrative worker, in Rambouillet, near Paris, France, April 23, 2021. REUTERS/Gonzalo Fuentes

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

Air India flight 185 arrives from New Delhi, narrowly beating the cut-off after Canada's government temporarily barred passenger flights from India and Pakistan for 30 days, at Vancouver International Airport in Richmond, British Columbia, Canada April 23, 2021. REUTERS/Jennifer Gauthier

Austria's Chancellor Sebastian Kurz, Vice Chancellor Werner Kogler and Health Minister Wolfgang Mueckstein attend a news conference on coronavirus disease (COVID-19) restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Austria's Chancellor Sebastian Kurz and Health Minister Wolfgang Mueckstein attend a news conference on coronavirus disease (COVID-19) restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Tennis - ATP 500 - Barcelona Open - Real Club de Tennis Barcelona, Barcelona, Spain - April 23, 2021 General view of Spain’s Rafael Nadal in action during his quarter final match against Great Britain’s Cameron Norrie REUTERS/Albert Gea

Austria's Chancellor Sebastian Kurz and Health Minister Wolfgang Mueckstein attend a news conference on coronavirus disease (COVID-19) restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Austria's Chancellor Sebastian Kurz and Health Minister Wolfgang Mueckstein attend a news conference on coronavirus disease (COVID-19) restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Austria's Health Minister Wolfgang Mueckstein attends a news conference on coronavirus disease (COVID-19) restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Austria's Health Minister Wolfgang Mueckstein attends a news conference on coronavirus disease (COVID-19) restrictions, in Vienna, Austria April 23, 2021. REUTERS/Lisi Niesner

Police officers secure the area where an attacker stabbed a female police administrative worker, in Rambouillet, near Paris, France, April 23, 2021. REUTERS/Gonzalo Fuentes

A police officer stands guard in the area where an attacker stabbed a female police administrative worker, in Rambouillet, near Paris, France, April 23, 2021. REUTERS/Gonzalo Fuentes

Tennis - ATP 500 - Barcelona Open - Real Club de Tennis Barcelona, Barcelona, Spain - April 23, 2021 Spain’s Rafael Nadal in action during his quarter final match against Great Britain’s Cameron Norrie REUTERS/Albert Gea

Tennis - ATP 500 - Barcelona Open - Real Club de Tennis Barcelona, Barcelona, Spain - April 23, 2021 Spain’s Rafael Nadal in action during his quarter final match against Great Britain’s Cameron Norrie REUTERS/Albert Gea

Pfizer CEO Albert Bourla talks during a press conference with European Commission President Ursula von der Leyen after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

Police officers secure the area where an attacker stabbed a female police administrative worker, in Rambouillet, near Paris, France, April 23, 2021. REUTERS/Gonzalo Fuentes

Pfizer CEO Albert Bourla talks during a press conference with European Commission President Ursula von der Leyen after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

Pfizer CEO Albert Bourla talks during a press conference with European Commission President Ursula von der Leyen after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

Pfizer CEO Albert Bourla talks during a press conference with European Commission President Ursula von der Leyen after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS

Pfizer CEO Albert Bourla talks during a press conference with European Commission President Ursula von der Leyen after a visit to oversee the production of the Pfizer-BioNtech COVID-19 vaccine at the factory of U.S. pharmaceutical company Pfizer in Puurs, Belgium April 23, 2021. John Thys /Pool via REUTERS