An employee shows her "Green Pass", a document showing proof of coronavirus disease (COVID-19) immunity, in an office in Rome, Italy, September 16, 2021. REUTERS/Yara Nardi

An employee shows her "Green Pass", a document showing proof of coronavirus disease (COVID-19) immunity, in an office in Rome, Italy, September 16, 2021. REUTERS/Yara Nardi

A tourist shows his "Green Pass", a document showing proof of coronavirus disease (COVID-19) immunity, as he enters the Colosseum, in Rome, Italy, September 16, 2021. REUTERS/Yara Nardi

A sign indicates where tourists must show their "Green Passes", a document showing proof of coronavirus disease (COVID-19) immunity, upon entering the Colosseum, in Rome, Italy, September 16, 2021. REUTERS/Yara Nardi

A security guard checks tourists' "Green Passes", a document showing proof of coronavirus disease (COVID-19) immunity, as they enter the Colosseum, in Rome, Italy, September 16, 2021. REUTERS/Yara Nardi

A tourist shows his "Green Pass", a document showing proof of coronavirus disease (COVID-19) immunity, as he enters the Colosseum, in Rome, Italy, September 16, 2021. REUTERS/Yara Nardi

Tourists line up to show their "Green Passes", a document showing proof of coronavirus disease (COVID-19) immunity, as they enter the Colosseum, in Rome, Italy, September 16, 2021. REUTERS/Yara Nardi

A specimen collection kit mailed in September 2021 to patients with blood cancers enrolled in the IMPACT study (Immune Profiling with Antibody-based COVID-19 Testing), being conducted by the Dana Farber Cancer Institute and Quest Diagnostics to shed light on how these patients' immune systems may interact with the SARS-CoV-2 virus or the vaccines, is seen in Chatham, New Jersey, U.S. September 10, 2021. REUTERS/Nancy Lapid

A specimen collection kit mailed in September 2021 to patients with blood cancers enrolled in the IMPACT study (Immune Profiling with Antibody-based COVID-19 Testing), being conducted by the Dana Farber Cancer Institute and Quest Diagnostics to shed light on how these patients' immune systems may interact with the SARS-CoV-2 virus or the vaccines, is seen in Chatham, New Jersey, U.S. September 10, 2021. REUTERS/Nancy Lapid

A specimen collection kit mailed in September 2021 to patients with blood cancers enrolled in the IMPACT study (Immune Profiling with Antibody-based COVID-19 Testing), being conducted by the Dana Farber Cancer Institute and Quest Diagnostics to shed light on how these patients' immune systems may interact with the SARS-CoV-2 virus or the vaccines, is seen in Chatham, New Jersey, U.S. September 10, 2021. REUTERS/Nancy Lapid

A student receives a dose of the Chinese Sinovac vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A man receives a dose of the vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A woman receives a dose of the vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A nurse prepares a dose of the Chinese Sinovac vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A nurse prepares a dose of the vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A man receives a dose of the vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

People wait before receiving the vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A student receives a dose of the vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A nurse shows a vial of the Chinese Sinovac vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

A student receives a dose of the Chinese Sinovac vaccine against coronavirus disease (COVID-19) at a mass immunization venue inside Cairo University, in Cairo, Egypt, September 8, 2021. REUTERS/Mohamed Abd El Ghany

Mimi Oset, 45, who has a visual disability and an immune-system illness, uses a nebuliser as she sits on her bed inside their house in the Sants neighborhood, amid the coronavirus disease (COVID-19) pandemic, in Barcelona, Spain, August 9, 2021. Picture taken August 9, 2021. REUTERS/Nacho Doce

Mimi Oset, 45, who has a visual disability and an immune-system illness, uses a nebuliser as she sits on her bed inside their house in the Sants neighborhood, amid the coronavirus disease (COVID-19) pandemic, in Barcelona, Spain, August 9, 2021. Picture taken August 9, 2021. REUTERS/Nacho Doce

Marina, 23 and her sister Ingrid, 9, daughters of Mimi Oset, 45, who has a visual disability and an immune-system illness, look at a laptop inside their house in the Sants neighborhood, amid the coronavirus disease (COVID-19) pandemic, in Barcelona, Spain, August 9, 2021. Picture taken August 9, 2021. REUTERS/Nacho Doce

Mimi Oset, 45, who has a visual disability and an immune-system illness, and her daughters Marina, 23, and Ingrid, 9, have breakfast inside their house in the Sants neighborhood, amid the coronavirus disease (COVID-19) pandemic, in Barcelona, Spain, August 9, 2021. Picture taken August 9, 2021. REUTERS/Nacho Doce

Marina, 23, and her sister Ingrid, 9, daughters of Mimi Oset, 45, who has a visual disability and an immune-system illness, draw a mandala while accompanied by Sonia, who is a family worker, inside their house in the Sants neighborhood, amid the coronavirus disease (COVID-19) pandemic, in Barcelona, Spain, August 9, 2021. Picture taken August 9, 2021. REUTERS/Nacho Doce

A man shows his coronavirus disease (COVID-19) health pass at a restaurant as France brings on tougher restrictions where a proof of immunity will now be required to access most public spaces and to travel by inter-city train, in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

A coronavirus disease (COVID-19) health pass poster is seen in a restaurant as France brings on tougher restrictions where a proof of immunity will now be required to access most public spaces and to travel by inter-city train, in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

Posters in a restaurant show the latest restrictions brought on by France, where a proof of immunity will now be required to access most of the public spaces and to travel by inter-city train, in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

A man shows his COVID-19 health pass at a restaurant as France brings on tougher restrictions where a proof of immunity will now be required to access most public spaces and to travel by inter-city train, in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

Coronavirus disease (COVID-19) health pass posters are seen outside a bar as France brings in tougher restrictions where a proof of immunity will be required to access most public spaces and to travel by inter-city train, in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

A coronavirus disease (COVID-19) health pass poster reading "Enter, Scan, Enjoy" is seen at a restaurant as France brings in tougher restrictions where a proof of immunity will be required to access most public spaces and to travel by inter-city train in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

Coronavirus disease (COVID-19) health pass posters are seen in a restaurant as France brings in tougher restrictions where a proof of immunity will be required to access public spaces and to travel by inter-city train in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

A coronavirus disease (COVID-19) health pass poster and a poster reading "Mandatory Mask" are seen outside a bar as France brings in tougher restrictions where a proof of immunity will be required to access most public spaces and to travel by inter-city train, in Nice, France, August 9, 2021. REUTERS/Eric Gaillard

A woman shows a COVID-19 health pass in a cafe as France brings in tougher restrictions where a proof of immunity will be required to access most of the public spaces or to travel on an inter-city train in Paris, France, August 9, 2021. REUTERS/Benoit Tessier

A man shows his COVID-19 health pass in a cafe as France brings in tougher restrictions where a proof of immunity will be required to access most of the public spaces or to travel on an inter-city train in Paris, France, August 9, 2021. REUTERS/Benoit Tessier

A customer's Green Pass (health pass) is checked before entry to a pizzeria as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities, in Rome, Italy, August 6, 2021. REUTERS/Remo Casilli

A woman has her Green Pass (health pass) checked before entering a pizzeria as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities, in Rome, Italy, August 6, 2021. REUTERS/Remo Casilli

A man has his Green Pass (health pass) checked before entering a pizzeria as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities, in Rome, Italy, August 6, 2021. REUTERS/Remo Casilli

A woman's Green Pass (health pass) is checked before entering a pizzeria as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities, in Rome, Italy, August 6, 2021. REUTERS/Remo Casilli

A man has his Green Pass (health pass) checked before entering a restaurant as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Remo Casilli

A man shows his Green Pass (health pass) before entering the Colosseum as Italy brings in tougher restrictions where proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

People have their Green Pass (health pass) checked before entering the Vatican Museums as Italy brings in tougher restrictions where where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

A woman has her Green Pass (health pass) checked before entering the Vatican Museums as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

A woman has her Green Pass (health pass) checked before entering the Vatican Museums as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

A woman shows her Green Pass (health pass) before entering the Vatican Museums as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

A man has his Green Pass (health pass) checked before entering the Vatican Museums as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

People have their Green Pass (health pass) checked before entering the Vatican Museums as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

People have their Green Pass (health pass) checked before entering the Vatican Museums as Italy brings in tougher restrictions where a proof of immunity will be required to access an array of services and leisure activities in Rome, Italy, August 6, 2021. REUTERS/Guglielmo Mangiapane

People wait in the observation room after receiving a dose of the Moderna vaccine against the coronavirus disease (COVID-19), a day before the wider Green Pass restrictions, where Italians will need proof of immunity to access an array of services and leisure activities, come into force, at the Music Auditorium in Rome, Italy, August 5, 2021. REUTERS/Guglielmo Mangiapane

A man receives a dose of the Moderna vaccine against the coronavirus disease (COVID-19), a day before the wider Green Pass restrictions, where Italians will need proof of immunity to access an array of services and leisure activities, come into force, at the Music Auditorium in Rome, Italy, August 5, 2021. REUTERS/Guglielmo Mangiapane

People receive a dose of the Moderna vaccine against the coronavirus disease (COVID-19), a day before the wider Green Pass restrictions, where Italians will need proof of immunity to access an array of services and leisure activities, come into force, at the Music Auditorium in Rome, Italy, August 5, 2021. REUTERS/Guglielmo Mangiapane

A woman receives a dose of the Moderna vaccine against the coronavirus disease (COVID-19), a day before the wider Green Pass restrictions, where Italians will need proof of immunity to access an array of services and leisure activities, come into force, at the Music Auditorium in Rome, Italy, August 5, 2021. REUTERS/Guglielmo Mangiapane

People receive a dose of the Moderna vaccine against the coronavirus disease (COVID-19), a day before the wider Green Pass restrictions, where Italians will need proof of immunity to access an array of services and leisure activities, come into force, at the Music Auditorium in Rome, Italy, August 5, 2021. REUTERS/Guglielmo Mangiapane

People wait in the observation room after receiving a dose of the Moderna vaccine against the coronavirus disease (COVID-19), a day before the wider Green Pass restrictions, where Italians will need proof of immunity to access an array of services and leisure activities, come into force, at the Music Auditorium in Rome, Italy, August 5, 2021. REUTERS/Guglielmo Mangiapane

A woman receives a dose of the Moderna vaccine against the coronavirus disease (COVID-19), a day before the wider Green Pass restrictions, where Italians will need proof of immunity to access an array of services and leisure activities, come into force, at the Music Auditorium in Rome, Italy, August 5, 2021. REUTERS/Guglielmo Mangiapane

A protestor dressed as Jesus Christ, holding a wooden cross reading "Vaccine kills your natural immunity", is surrounded by French Gendarmes on the Champs Elysees Avenue after clashes on the sidelines of a demonstration against France's restrictions to fight the coronavirus disease (COVID-19) outbreak, in Paris, France, July 24, 2021. REUTERS/Benoit Tessier

A protestor dressed as Jesus Christ, holding a wooden cross reading "Vaccine kills your natural immunity", is surrounded by French Gendarmes on the Champs Elysees Avenue after clashes on the sidelines of a demonstration against France's restrictions to fight the coronavirus disease (COVID-19) outbreak, in Paris, France, July 24, 2021. REUTERS/Benoit Tessier TPX IMAGES OF THE DAY

A protestor dressed as Jesus Christ, holding a wooden cross reading "Vaccine kills your natural immunity" is surrounded by French Gendarmes on the Champs Elysees Avenue after clashes on the sidelines of a demonstration against France's restrictions to fight the coronavirus disease (COVID-19) outbreak, in Paris, France, July 24, 2021. REUTERS/Benoit Tessier