Fourth year medical students observe physical distancing while seated in a classroom, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

A fourth year medical student performs phlebotomy on a fellow student, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

Fourth year medical students perform phlebotomy, following the return of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

Fourth year medical students perform episiotomy on a model, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

Dr. Clifton Pe demonstrates auscultation of heart and lung sounds through a medical mannequin, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

Fourth year medical students observe social distancing as they line up before entering the building, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

A medical professor demonstrates three bottle system for chest tube thoracotomy to fourth year medical students, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

Dr. Jocelyn Mariano demonstrates childbirth delivery to fourth year medical students, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

A fourth year medical student performs breast examination on a model, following the resumption of limited face-to-face classes amid the coronavirus disease (COVID-19), at the University of Santo Tomas, in Manila, Philippines, June 14, 2021. REUTERS/Lisa Marie David

A child wearing a face mask counts sheets of a notebook during a class at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

A child holds his parents' permission to attend classes while waiting in line to enter the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

Children are seen at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

A doctor checks the body temperature of a child arriving at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

Parents and their children queue to enter the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

A child receives hand sanitizer while arriving at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

Children walk in line toward their classroom at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

Children stretch before entering their classrooms at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

A child raises his hands during a class at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

A teacher conducts a class at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalizations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

Children play with a balloon at the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

A man decorates the entrance of the Ignacio Zaragoza elementary school as Mexico City's authorities resumed in-person classes today after a downward trend in the number of infections and hospitalisations of the coronavirus disease (COVID-19), in Mexico City, Mexico June 7, 2021. REUTERS/Luis Cortes

Planes sit on the tarmac at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, Algeria June 1, 2021. REUTERS/Ramzi Boudina

Airport employees wearing protective gear stand as passengers traveling from Paris arrive at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, Algeria June 1, 2021. REUTERS/Ramzi Boudina

A man gestures as passengers traveling from Paris arrive at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, Algeria June 1, 2021. REUTERS/Ramzi Boudina

An airport employee wearing protective gear stands as passengers traveling from Paris arrive at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, Algeria June 1, 2021. REUTERS/Ramzi Boudina

Passengers traveling from Paris push their luggage upon arrival at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, Algeria June 1, 2021. REUTERS/Ramzi Boudina

A passenger traveling from Paris arrives at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, Algeria June 1, 2021. REUTERS/Ramzi Boudina

General view shows Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, in Algiers, Algeria June 1, 2021. REUTERS/Ramzi Boudina

Passengers push their luggage at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, in Algiers, Algeria June 1, 2021. REUTERS/Ramzi Boudina

People queue to buy airline tickets inside Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, in Algiers, Algeria June 1, 2021. REUTERS/Ramzi Boudina

Passengers look at a departures board at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, in Algiers, Algeria June 1, 2021. REUTERS/Ramzi Boudina

Passengers queue at Algiers Airport, as Algeria resumed some international flights, amid the coronavirus disease (COVID-19) outbreak, in Algiers, Algeria June 1, 2021. REUTERS/Ramzi Boudina

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann TPX IMAGES OF THE DAY

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

People attend the massive experimental concert "Ambition Live Again", organised by Assistance Publique-Hopitaux de Paris (AP-HP) and music industry union Prodiss to assess health risks associated with resuming large-scale public gatherings since the beginning of the coronavirus disease (COVID-19) pandemic, at Paris Accor Arena in Paris, France, May 29, 2021. REUTERS/Christian Hartmann

FILE PHOTO: Soccer Football - La Liga Santander - Real Madrid v Villarreal - Alfredo Di Stefano Stadium, Madrid, Spain - July 16, 2020 Real Madrid coach Zinedine Zidane celebrates with the trophy after winning La Liga, as play resumes behind closed doors following the outbreak of the coronavirus disease (COVID-19) REUTERS/Sergio Perez/File Photo

Austrian Minister for Climate Action and Mobility Leonore Gewessler looks outside a Nightjet train of Austrian Federal Railways OeBB ahead of departure as it resumes travel operation amid the coronavirus disease (COVID-19) outbreak, at the main station in Vienna, Austria, May 24, 2021. REUTERS/Lisi Niesner

Passengers are reflected in the window of a Nightjet train of Austrian Federal Railways OeBB ahead of departure as it resumes travel operation amid the coronavirus disease (COVID-19) outbreak, at the main station in Vienna, Austria, May 24, 2021. REUTERS/Lisi Niesner

A Nightjet train of Austrian Federal Railways OeBB departs as it resumes travel operation amid the coronavirus disease (COVID-19) outbreak, at the main station in Vienna, Austria, May 24,2021. REUTERS/Lisi Niesner

Passengers wait on the platform before boarding a Nightjet train of Austrian Federal Railways OeBB ahead of departure as it resumes travel operation amid the coronavirus disease (COVID-19) outbreak, at the main station in Vienna, Austria, May 24,2021. REUTERS/Lisi Niesner

Passengers look outside the window of a Nightjet train of Austrian Federal Railways OeBB ahead of departure as it resumes travel operation amid the coronavirus disease (COVID-19) outbreak, at the main station in Vienna, Austria, May 24, 2021. REUTERS/Lisi Niesner

A Nightjet train of Austrian Federal Railways OeBB departs as it resumes travel operation amid the coronavirus disease (COVID-19) outbreak, at the main station in Vienna, Austria, May 24, 2021. REUTERS/Lisi Niesner

Austrian Minister for Climate Action and Mobility Leonore Gewessler looks outside a Nightjet train of Austrian Federal Railways OeBB ahead of departure as it resumes travel operation amid the coronavirus disease (COVID-19) outbreak, at the main station in Vienna, Austria, May 24, 2021. REUTERS/Lisi Niesner