A police officer wearing a protective face mask walks past the closed entrance of the Athens' Polytechnic School, as the Greek government banned the annual march marking the anniversary of a 1973 student revolt against the then military junta due to the coronavirus disease (COVID-19) pandemic, in Athens, Greece, November 17, 2020. REUTERS/Alkis Konstantinidis

A wreath is placed on the closed entrance of the Athens' Polytechnic School, as the Greek government banned the annual march marking the anniversary of a 1973 student revolt against the then military junta due to the coronavirus disease (COVID-19) pandemic, in Athens, Greece, November 17, 2020. REUTERS/Alkis Konstantinidis

Hong Kong's Commissioner of Police Chris Ping-keung Tang walks outside Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 19, 2019. Picture taken November 19, 2019. REUTERS/Adnan Abidi To match Special Report HONGKONG-PROTESTS/SECURITY-POLICE

A health worker holds a box with a sign reading "Transport of samples COVID-19" at the National Polytechnic Institute (IPN) where test are being taken, as the coronavirus disease (COVID-19) outbreak continues, in Mexico City, Mexico June 17, 2020. REUTERS/Henry Romero

A member of biological sciences of the National Polytechnic Institute (IPN) tests a woman for the coronavirus disease (COVID-19) at the university, as the coronavirus disease (COVID-19) outbreak continues, in Mexico City, Mexico June 17, 2020. REUTERS/Henry Romero

Members of biological sciences of the National Polytechnic Institute (IPN) test people for the coronavirus disease (COVID-19) at the university, as the coronavirus disease (COVID-19) outbreak continues, in Mexico City, Mexico June 17, 2020. REUTERS/Henry Romero

A member of biological sciences of the National Polytechnic Institute (IPN) tests a woman for the coronavirus disease (COVID-19) at the university, as the coronavirus disease (COVID-19) outbreak continues, in Mexico City, Mexico June 17, 2020. REUTERS/Henry Romero

Members of biological sciences of the National Polytechnic Institute (IPN) test people for the coronavirus disease (COVID-19) at the university, as the coronavirus disease (COVID-19) outbreak continues, in Mexico City, Mexico June 17, 2020. REUTERS/Henry Romero

A member of biological sciences of the National Polytechnic Institute (IPN) tests a woman for the coronavirus disease (COVID-19) at the university, as the coronavirus disease (COVID-19) outbreak continues, in Mexico City, Mexico June 17, 2020. REUTERS/Henry Romero

A doctor shows the drug Oral Transferon, which is part of a protocol at the National Polytechnic Institute (IPN) to evaluate the effects of its treatment in patients with the coronavirus disease (COVID-19), as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

A woman signs herself into a clinical protocol to be treated with the drug Oral Transferon, which aims to evaluate the effects of its treatment in patients with the coronavirus disease (COVID-19), at the National Polytechnic Institute (IPN), as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

A member of biological sciences of the National Polytechnic Institute (IPN) tests a woman for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

Members of biological sciences of the National Polytechnic Institute (IPN) test men for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso TPX IMAGES OF THE DAY

A member of biological sciences of the National Polytechnic Institute (IPN) tests a man for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

A member of biological sciences of the National Polytechnic Institute (IPN) tests a man for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

Members of biological sciences of the National Polytechnic Institute (IPN) test men for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

A member of biological sciences of the National Polytechnic Institute (IPN) tests a man for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

A member of biological sciences of the National Polytechnic Institute (IPN) rests before testing patients for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

A member of biological sciences of the National Polytechnic Institute (IPN) tests a man for the coronavirus disease (COVID-19) at the university, as the outbreak of the COVID-19 continues, in Mexico City, Mexico May 19, 2020. REUTERS/Carlos Jasso

A man clears debris following the clashes between police and anti-government protester after a two week campus siege of the Polytechnic University in Hong Kong, China, November 16, 2019. Reuters has been awarded the 2020 Pulitzer Prize in Breaking News Photography for Hong Kong protests. REUTERS/Adnan Abidi TPX IMAGES OF THE DAY

A prototype of a ventilator is seen at a polytechnic laboratory amid an outbreak of the coronavirus disease (COVID-19), in Thies, Senegal April 7, 2020. Picture taken April 7,2020. REUTERS/Zohra Bensemra

Scientist Dr Ibrahima Gueye talks to a journalist as he stands beside a prototype of a ventilator he developed with a team, at a polytechnic laboratory, amid an outbreak of the coronavirus disease (COVID-19), in Thies, Senegal April 7, 2020. Picture taken April 7,2020. REUTERS/Zohra Bensemra

Scientist Dr Ibrahima Gueye talks to a journalist as he stands beside a prototype of a ventilator he developed with a team, at a polytechnic laboratory, amid an outbreak of the coronavirus disease (COVID-19), in Thies, Senegal April 7, 2020. Picture taken April 7,2020. REUTERS/Zohra Bensemra

Two frontline lovers in full body gear hug each other in the besieged Hong Kong Polytechnic University (PolyU) campus that had been on lockdown for a week in Hong Kong, China on November 18, 2019. Picture taken November 18, 2019. REUTERS/Jessie Pang

Graffiti with Chinese words “Why have universities become battlegrounds?” is seen at he Hong Kong Polytechnic University (PolyU) campus that has been on lockdown for a week in Hong Kong, China November 23, 2019. Picture taken November 23, 2019. REUTERS/Jessie Pang

A rainbow forms near the bridge where protesters made a daring escape past walls of riot police at the Hong Kong Polytechnic University (PolyU) campus that has been on lockdown for a week in Hong Kong, China November 19, 2019. Picture taken November 19, 2019. REUTERS/Jessie Pang

A decorated statue is seen in a building inside of a nearly empty Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

An abandoned shoe lays on a graffitied ground inside of a nearly empty Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

A classroom that was converted into a living space by desperate protesters, trapped inside of Hong Kong Polytechnic University (PolyU) can be seen on the campus under siege by the police in Hong Kong, China, November 22, 2019. Picture taken November 22, 2019. REUTERS/Leah Millis

A sign and graffiti are seen inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

People walk through a courtyard inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

A wrecked umbrella, gloves, arrows and other items are seen covered in leaves and dried blue substance from a police water cannon inside of the Hong Kong Polytechnic University (PolyU), the campus under siege by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Trampled protest signs can be seen on the ground inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

An abandoned umbrella and a bow lay on the ground inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

A glove lays abandoned on graffitied ground inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Workers can be seen repairing the sidewalk outside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Charred papers lay on the ground inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Zip-ties, old crackers, medical supplies, a fire blanket and a power drill are among items that lay abandoned on a table inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

A zip-tie and an arrow lay abandoned inside of Hong Kong Polytechnic University (PolyU) during a police siege of the campus in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

An abandoned umbrella and shards of glass lay on the ground inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Unused Molotov cocktails and bricks can be seen from the inside of the Hong Kong Polytechnic University (PolyU) as workers repair the sidewalk outside of the campus under siege by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Hundreds of unused Molotov cocktails sit abandoned inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

An electrolyte drink, cigarettes, old food and an unused Molotov cocktail lay abandoned on a stair inside of Hong Kong Polytechnic University (PolyU) as the campus continues to be closed by police in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Protesters sing Glory to Hong Kong outside of Polytechnic University (PolyU) while police keep it under siege in Hong Kong, China, November 25, 2019. Picture taken November 25, 2019. REUTERS/Leah Millis

First aid cards for patients lay strewn in a rock pile near the entrance, inside of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Unused Molotov cocktails can be seen from the inside of the Hong Kong Polytechnic University (PolyU) as a police officer walks by outside of the campus under siege in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

Protesters sing Glory to Hong Kong outside of Polytechnic University (PolyU) while police keep it under siege in Hong Kong, China, November 25, 2019. Picture taken November 25, 2019. REUTERS/Leah Millis

An abandoned rock-breaking station can be seen along with a fire extinguisher near the entrance, inside of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 27, 2019. Picture taken November 27, 2019. REUTERS/Leah Millis

A shopkeeper watches protesters outside the Polytechnic University (PolyU) in Hong Kong, China, November 25, 2019. Picture taken November 25, 2019. REUTERS/Leah Millis

Police shine a flashlight on the face of a protester outside of Polytechnic University (PolyU) while police keep it under siege in Hong Kong, China, November 25, 2019. Picture taken November 25, 2019.REUTERS/Leah Millis

A member of the news media sleeps while another works in a classroom inside of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 23, 2019. Picture taken November 23, 2019. REUTERS/Leah Millis

Members of the news media interview a remaining protester who is trapped inside of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 23, 2019. Picture taken November 23, 2019. REUTERS/Leah Millis

Protesters clash with police outside Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 17, 2019. REUTERS/Thomas Peter/File Photo SEARCH "HONG KONG POY" FOR THIS STORY. SEARCH "REUTERS POY" FOR ALL BEST OF 2019 PACKAGES. TPX IMAGES OF THE DAY.

Protesters stand amid a fire at Hong Kong Polytechnic University (PolyU) during an anti-government protest in Hong Kong, China November 18, 2019. REUTERS/Athit Perawongmetha/File Photo SEARCH "HONG KONG POY" FOR THIS STORY. SEARCH "REUTERS POY" FOR ALL BEST OF 2019 PACKAGES. TPX IMAGES OF THE DAY.

A protester tries to escape from a sewage tunnel inside the Hong Kong Polytechnic University campus during protests in Hong Kong, China, November 19, 2019. REUTERS/Adnan Abidi/File Photo SEARCH "HONG KONG POY" FOR THIS STORY. SEARCH "REUTERS POY" FOR ALL BEST OF 2019 PACKAGES. TPX IMAGES OF THE DAY.

A protester holds a bow and arrow during clashes with police outside Hong Kong Polytechnic University (PolyU), in Hong Kong, China, November 17, 2019. REUTERS/Athit Perawongmetha/File Photo SEARCH "HONG KONG POY" FOR THIS STORY. SEARCH "REUTERS POY" FOR ALL BEST OF 2019 PACKAGES. TPX IMAGES OF THE DAY.

Pak (2nd R), an anti-government protester, checks his mobile phone as he guards a bridge outside Polytechnic University in Hong Kong, November 16, 2019. Picture taken November 16, 2019. REUTERS/Adnan Abidi To match Special Report HONGKONG-PROTESTS/RADICAL

Pak (C), an anti-government protester, checks his mobile phone as he guards a bridge outside Polytechnic University in Hong Kong, November 16, 2019. Picture taken November 16, 2019. REUTERS/Adnan Abidi To match Special Report HONGKONG-PROTESTS/RADICAL