Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain TPX IMAGES OF THE DAY

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Members of the Bangladesh Police wear protective masks as they join a yoga session to boost their immune systems as the coronavirus disease (COVID-19) outbreak continues, in Dhaka, Bangladesh June 14, 2020. REUTERS/Mohammad Ponir Hossain

Alessandra Said, 45, a doctor at Emergency Rescue Service (SAMU) takes vitamins to keep her immunity high after working 12 hours at SAMU, during the spread of the coronavirus disease (COVID-19), at her home in Manaus, Brazil May 12, 2020. Picture taken May 12, 2020. REUTERS/Bruno Kelly

A demonstrator holding a sign reading "Grandparents for Herd Immunity" as protestors rally against coronavirus disease (COVID-19) restrictions during a rally held outside the Pennsylvania State Capitol Building in Harrisburg, Pennsylvania, U.S., May 15, 2020. REUTERS/Jonathan Ernst

Wojciech Glac, neurobiologist at the University of Gdansk, explains how to play a board game he invented called "Infection" on the novel coronavirus and the human immune system, during an interview with Reuters as the spread of the coronavirus disease (COVID-19) continues in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

Wojciech Glac, neurobiologist at the University of Gdansk, gestures during an interview with Reuters about a board game he invented called "Infection" on the novel coronavirus and the human immune system, as the spread of the coronavirus disease (COVID-19) continues in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

Wojciech Glac, neurobiologist at the University of Gdansk, throws board game pieces as he poses for a photograph during an interview with Reuters about a board game he invented called "Infection" on the novel coronavirus and the human immune system, as the spread of the coronavirus disease (COVID-19) continues, in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

Wojciech Glac, neurobiologist at the University of Gdansk, shows a board game piece depicting a virus during an interview with Reuters about a board game he invented called "Infection" on the novel coronavirus and the human immune system, as the spread of the coronavirus disease (COVID-19) continues in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

Wojciech Glac, neurobiologist at the University of Gdansk, looks on during an interview with Reuters about a board game he invented called "Infection" on the novel coronavirus and the human immune system, as the spread of the coronavirus disease (COVID-19) continues in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

Wojciech Glac, neurobiologist at the University of Gdansk, shows a board game he invented called "Infection" on the novel coronavirus and the human immune system, during an interview with Reuters, as the spread of the coronavirus disease (COVID-19) continues, in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

A board game on the novel coronavirus and the human immune system called "Infection", invented by Wojciech Glac, a neurobiologist at the University of Gdansk, is pictured, as the spread of the coronavirus disease (COVID-19) continues in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

Karolina Topa, a biology teacher, and her boyfriend Marek Grudkowski play the "Infection" board game about the novel coronavirus and the human immune system, invented by Gdansk University neurobiologist Wojciech Glac, as the spread of the coronavirus disease (COVID-19) continues in Gdansk, Poland, May 13, 2020. Picture taken May 13, 2020. REUTERS/Matej Leskovsek

Wojciech Glac, neurobiologist at the University of Gdansk, shows a board game piece depicting a virus during an interview with Reuters about a board game he invented called "Infection" on the novel coronavirus and the human immune system, as the spread of the coronavirus disease (COVID-19) continues, in Wejherowo, Poland, May 12, 2020. Picture taken May 12, 2020. REUTERS/Matej Leskovsek

Karolina Topa, a biology teacher, uses the "Infection" board game about the novel coronavirus and the human immune system, invented by Gdansk University neurobiologist Wojciech Glac, during an online class with her pupils, as the spread of the coronavirus disease (COVID-19) continues in Gdansk, Poland, May 13, 2020. Picture taken May 13, 2020. REUTERS/Matej Leskovsek

Karolina Topa, a biology teacher, and her boyfriend Marek Grudkowski play the "Infection" board game about the novel coronavirus and the human immune system, invented by Gdansk University neurobiologist Wojciech Glac, as the spread of the coronavirus disease (COVID-19) continues in Gdansk, Poland, May 13, 2020. Picture taken May 13, 2020. REUTERS/Matej Leskovsek TPX IMAGES OF THE DAY

Karolina Topa, a biology teacher, uses the "Infection" board game about the novel coronavirus and the human immune system, invented by Gdansk University neurobiologist Wojciech Glac, during an online class with her pupils, as the spread of the coronavirus disease (COVID-19) continues in Gdansk, Poland, May 13, 2020. Picture taken May 13, 2020. REUTERS/Matej Leskovsek

Northwell Health medical workers do antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Northwell Health medical workers do antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Northwell Health medical workers do antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Northwell Health medical workers wait for people to have blood drawn for antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

People wait in a socially distanced line to have their blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Quannesha Lewis, 30, waits in a socially distanced line to have her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleto

Quannesha Lewis, 30, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) as her mother Pamela Douglas, 51, watches at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Quannesha Lewis, 30, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) as her mother Pamela Douglas, 51, watches at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Shalonda Williams-Hampton, 32, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Shalonda Williams-Hampton, 32, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Shalonda Williams-Hampton, 32, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Shalonda Williams-Hampton, 32, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Shalonda Williams-Hampton, 32, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Shalonda Williams-Hampton, 32, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Shalonda Williams-Hampton, 32, has her blood taken by Northwell Health medical workers for the antibody tests that detect whether a person has developed immunity to the coronavirus disease (COVID-19) at the First Baptist Cathedral of Westbury in Westbury, New York, U.S., May 13, 2020. REUTERS/Shannon Stapleton

Erma Aldaba and daughter Angie Leija stand near the grave of Aldaba's son Johnny Leija, who died in hospital following an encounter with the police, at a cemetery near Madill, Oklahoma, U.S. April 11, 2019. Picture taken April 11, 2019. To match Special Report USA-POLICE/IMMUNITY-SCOTUS. REUTERS/Andrew Chung

Erma Aldaba sits in her home, wearing a T-shirt emblazoned with the image of her son Johnny Leija, who died in hospital after a deadly encounter with the police, in Madill, Oklahoma, U.S. April 11, 2019. Picture taken April 11, 2019. To match Special Report USA-POLICE/IMMUNITY-SCOTUS. REUTERS/Andrew Chung

Marshall County Deputy Sheriff Steve Beebe, one of the three officers trying to subdue Johnny Leija when he died, stands next to a police car in Madill, Oklahoma, U.S. April 11, 2019. Picture taken April 11, 2019. To match Special Report USA-POLICE/IMMUNITY-SCOTUS. REUTERS/Andrew Chung

Winston Casey of Arlington, VA, who has no spleen, an important immune system organ, wears a mask to protect against the coronavirus disease (COVID-19) on the practice range before his round of golf at Westfields Golf Club in Clifton,Virginia, U.S., April 21, 2020. REUTERS/Kevin Lamarque

Nicole Scovil, a nurse in oncology, poses for a portrait at the University of Washington Medical Center - Montlake during the coronavirus disease (COVID-19) outbreak, in Seattle, Washington, U.S. April 15, 2020. "These past couple weeks have been exceptionally scary for our patients since nearly all of them have no immune system. I?m really missing patients I haven?t been able to visit, as they?re high risk and I work with Covid patients," she says. REUTERS/David Ryder

A man wearing a face mask sits along rail tracks to enjoy sunshine as they believe it improves their immunity, during the imposition of large-scale social restrictions by the government to prevent the spread of the coronavirus disease (COVID-19) in Jakarta, Indonesia, April 12, 2020. REUTERS/Willy Kurniawan

People wearing face masks are seen along rail tracks enjoying sunshine as they believe it improves their immunity, during the imposition of large-scale social restrictions by the government to prevent the spread of the coronavirus disease (COVID-19) in Jakarta, Indonesia, April 12, 2020. REUTERS/Willy Kurniawan

A woman wearing a face mask sits along rail tracks to enjoy sunshine as they believe it improves their immunity, during the imposition of large-scale social restrictions by the government to prevent the spread of the coronavirus disease (COVID-19) in Jakarta, Indonesia, April 12, 2020. REUTERS/Willy Kurniawan

A new blood test to check for immunity for coronavirus disease (COVID-19) is seen at a lab in Los Angeles, California, U.S. March 26, 2020. REUTERS/Alan Devall

A new blood test to check for immunity for coronavirus disease (COVID-19) is seen at a lab in Los Angeles, California, U.S. March 26, 2020. REUTERS/Alan Devall

A new blood test to check for immunity for coronavirus disease (COVID-19) is seen at a lab in Los Angeles, California, U.S. March 26, 2020. REUTERS/Alan Devall

Seniors are pictured at a Safeway grocery store, which is asking customers to reserve the hours 7 am to 9 am on Tuesdays and Thursdays for seniors, pregnant women and people with compromised immune systems, during the coronavirus disease (COVID-19) outbreak, in Seattle, Washington, U.S. March 19, 2020. REUTERS/Jason Redmond

Shoppers exit a Safeway grocery store, which is asking customers to reserve the hours 7 am to 9 am on Tuesdays and Thursdays for seniors, pregnant women and people with compromised immune systems, during the coronavirus disease (COVID-19) outbreak, in Seattle, Washington, U.S. March 19, 2020. REUTERS/Jason Redmond

A notice is pictured at a Safeway grocery store asking customers to reserve the hours 7 am to 9 am on Tuesdays and Thursdays for seniors, pregnant women and people with compromised immune systems, during the coronavirus disease (COVID-19) outbreak, in Seattle, Washington, U.S. March 19, 2020. REUTERS/Jason Redmond

Shoppers enter a Safeway grocery store, which is asking customers to reserve the hours 7 am to 9 am on Tuesdays and Thursdays for seniors, pregnant women and people with compromised immune systems, during the coronavirus disease (COVID-19) outbreak, in Seattle, Washington, U.S. March 19, 2020. REUTERS/Jason Redmond

Tom Fitzpatrick loads groceries into his car at a Safeway grocery store, which is asking customers to reserve the hours 7 am to 9 am on Tuesdays and Thursdays for seniors, pregnant women and people with compromised immune systems, during the coronavirus disease (COVID-19) outbreak, in Seattle, Washington, U.S. March 19, 2020. REUTERS/Jason Redmond

Jean Wilson, 62, waves while exercising with her Shichon dog, Dottie, amidst coronavirus-related event cancelations at Fenney Recreation Center in The Villages, Florida, U.S., ahead of the upcoming Democratic primary March 14, 2020. Wilson says: "I know it's serious in Italy and I understand we need to contain it. The two-week quarantine for everyone is a good thing. But because so far there are no known cases in The Villages and our county, I'm not worried about it. I'm 62-years-old and I don't take the flu shot. I want my body to build up immunities on my own." REUTERS/Yana Paskova

(L-R) Jean Wilson, 62, exercises with her Shichon dogs, Dottie and Yogi, amidst coronavirus-related event cancellations at Fenney Recreation Center in The Villages, Florida, U.S., ahead of the upcoming Democratic primary March 14, 2020. Wilson says: "I know it's serious in Italy and I understand we need to contain it. The two-week quarantine for everyone is a good thing. But because so far there are no known cases in The Villages and our county, I'm not worried about it. I'm 62-years-old and I don't take the flu shot. I want my body to build up immunities on my own." REUTERS/Yana Paskova

Director of the Center for the National Center for Immunization and Respiratory Diseases (NCIRD) doctor Nancy Messonnier speaks about the public health response to the outbreak of the coronavirus during a news conference at the Department of Health and Human Services (HHS) in Washington, U.S., January 28, 2020. REUTERS/Amanda Voisard

Director of the Center for the National Center for Immunization and Respiratory Diseases (NCIRD) doctor Nancy Messonnier speaks about the public health response to the outbreak of the coronavirus during a news conference at the Department of Health and Human Services (HHS) in Washington, U.S., January 28, 2020. REUTERS/Amanda Voisard.

Director of the Center for the National Center for Immunization and Respiratory Diseases (NCIRD) doctor Nancy Messonnier speaks about the public health response to the outbreak of the coronavirus during a news conference at the Department of Health and Human Services (HHS) in Washington, U.S., January 28, 2020. REUTERS/Amanda Voisard.

A lawmaker looks on before a session of Ukrainian parliament in Kiev, Ukraine August 29, 2019. Picture taken August 29, 2019. REUTERS/Gleb Garanich TPX IMAGES OF THE DAY