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

People are reflected in a window while waiting to receive a vaccine against the coronavirus disease (COVID-19) as a woman is being inoculated by a healthcare worker, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

A person receives a vaccine against the coronavirus disease (COVID-19), in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

People stand in line waiting to receive the vaccine against the coronavirus disease (COVID-19), in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

People receive vaccines against the coronavirus disease (COVID-19) at the Instituto Americano, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

A woman receives a vaccine against the coronavirus disease (COVID-19) at the Instituto Americano, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

People receive vaccines against the coronavirus disease (COVID-19) at the Instituto Americano, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

People receive vaccines against the coronavirus disease (COVID-19) at the Instituto Americano, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

People are reflected in a window while waiting to receive a vaccine against the coronavirus disease (COVID-19) as a healthcare worker prepares a vaccine, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

People receive vaccines against the coronavirus disease (COVID-19) as others are reflected in a window waiting to be inoculated, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

People are reflected in a window while waiting to receive a vaccine against the coronavirus disease (COVID-19) as healthcare workers prepare vaccines, in La Paz, Bolivia July 18, 2021. REUTERS/Claudia Morales

Atryom Subbotin, IT entrepreneur, shows a gold plate with a personal QR code showing he has been vaccinated, had an infection indicating immunity or have recently tested negative, mandatory requirement to be served in cafes and restaurants, in Moscow, Russia July 8, 2021. REUTERS/Alexander Reshetnikov

UPDATE clarifies axis label An Oxford University study found that a second dose of the Oxford-AstraZeneca COVID-19 vaccine can be delayed and lead to an enhanced immune response.

A graffiti reading "Herd immunity" is seen during the outbreak of the coronavirus disease (COVID-19) in Santiago, Chile June 7, 2021. REUTERS/Ivan Alvarado

An elderly woman wearing a protective face mask against COVID-19, leaves after receiving vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

A man receives a dose of the China's Sinopharm vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

People arrive for vaccinations against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

An employee wearing a protective face mask against COVID-19, waits for people who want to vaccinate against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

Health staff members wearing protective face masks against COVID-19, wait for people who want to vaccinate against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

People wait for vaccinations against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

A nurse shows a vial of the AstraZeneca vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

A man receives a dose of vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

A nurse prepares a dose of the AstraZeneca vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 5, 2021. REUTERS/Amr Abdallah Dalsh

A person shows her Hungarian coronavirus disease (COVID-19) immunity card to take part in a protest against the planned Chinese Fudan University campus in Budapest, Hungary, June 5, 2021. REUTERS/Bernadett Szabo

People show their Hungarian coronavirus disease (COVID-19) immunity cards to take part in a protest against the planned Chinese Fudan University campus in Budapest, Hungary, June 5, 2021. REUTERS/Bernadett Szabo

Catalan MEP Carles Puigdemont attends a joint news conference with Catalan MEPs Antoni Comin and Clara Ponsati regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEPs Antoni Comin, Carles Puigdemont and Clara Ponsati leave after a joint news conference regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEP Clara Ponsati speaks during a joint news conference with Catalan MEPs Carles Puigdemont and Antoni Comin regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEP Carles Puigdemont puts on his protective face mask during a joint news conference with Catalan MEPs Antoni Comin and Clara Ponsati regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEP Antoni Comin speaks during a joint news conference with Catalan MEPs Carles Puigdemont and Clara Ponsati regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEP Antoni Comin speaks during a joint news conference with Catalan MEPs Carles Puigdemont and Clara Ponsati regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEP Carles Puigdemont looks on during a joint news conference with Catalan MEPs Antoni Comin and Clara Ponsati regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEP Carles Puigdemont gestures during a joint news conference with Catalan MEPs Antoni Comin and Clara Ponsati regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEPs Antoni Comin, Carles Puigdemont and Clara Ponsati hold a joint news conference regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEPs Antoni Comin and Carles Puigdemont hold a joint news conference regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

Catalan MEPs Antoni Comin, Carles Puigdemont and Clara Ponsati hold a joint news conference regarding their immunity at the European Parliament, in Brussels, Belgium June 3, 2021. REUTERS/Yves Herman

People react after receiving the first shot of vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A man wearing a protective mask against COVID-19, leaves after receiving a vaccine against the coronavirus disease at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A worker wearing a protective mask against COVID-19, reacts after receiving a vaccine against the coronavirus disease, at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A worker cleans in front of a poster of Egypt's President Abdel Fattah al-Sisi that reads,"National campaign for coronavirus vaccine" at a mass immunization venue inside Cairo's International Exhibition Center against the coronavirus disease (COVID-19) in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

An employee drives people who receive vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A nurse shows a vial of China's Sinopharm vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

Health staff members collect information at a mass immunization venue during vaccination against the coronavirus disease (COVID-19), inside International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A nurse shows a vial of the AstraZeneca vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

An elderly woman arrives to receive vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

People wait to receive a shot of the COVID-19 vaccine at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

An elderly man receives a dose of China's Sinopharm vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A man receives a dose of the AstraZeneca vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

People wait to receive a shot of the COVID-19 vaccine at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A nurse administers a dose of the AstraZeneca vaccine against the coronavirus disease (COVID-19) at a mass immunization venue inside Cairo's International Exhibition Center in Cairo, Egypt June 2, 2021. REUTERS/Amr Abdallah Dalsh

A man rides his bicycle outside a vaccination centre at the University of Malta, after authorities announced that Malta had achieved herd immunity with 70% of the population having received at least one vaccine dose against the coronavirus disease (COVID-19), in Msida, Malta May 24, 2021. REUTERS/Darrin Zammit Lupi

People walk outside a vaccination centre at the University of Malta, after authorities announced that Malta had achieved herd immunity with 70% of the population having received at least one vaccine dose against the coronavirus disease (COVID-19), in Msida, Malta May 24, 2021. REUTERS/Darrin Zammit Lupi

People walk outside a vaccination centre at the University of Malta, after authorities announced that Malta had achieved herd immunity with 70% of the population being receiving at least one vaccine dose against the coronavirus disease (COVID-19), in Msida, Malta May 24, 2021. REUTERS/Darrin Zammit Lupi

Reverend Jesse Jackson eats ice cream with Ben Cohen and Jerry Greenfield, of Ben and Jerry's Ice Cream, at Campaign to End Qualified Immunity in front of the Supreme Court in Washington, U.S., May 20, 2021. REUTERS/Ken Cedeno

Ben Cohen, of Ben and Jerry's Ice Cream, holds up a copy of his book 'Above The Law' at Campaign to End Qualified Immunity in front of the Supreme Court in Washington, U.S., May 20, 2021. REUTERS/Ken Cedeno

Reverend Jesse Jackson greets Ben Cohen and Jerry Greenfield, of Ben and Jerry's Ice Cream, at Campaign to End Qualified Immunity in front of the Supreme Court in Washington, U.S., May 20, 2021. REUTERS/Ken Cedeno

Ben Cohen, of Ben and Jerry's Ice Cream, hands out pamphlets at Campaign to End Qualified Immunity in front of the Supreme Court in Washington, U.S., May 20, 2021. REUTERS/Ken Cedeno