A woman gets an influenza vaccine at a hospital in Seoul, South Korea, October 23, 2020. REUTERS/Kim Hong-Ji 

A man gets an influenza vaccine at a branch of the Korea Association of Health Promotion in Seoul, South Korea, October 23, 2020. REUTERS/Kim Hong-Ji 

People fill in a mandatory document to get an influenza vaccine at a branch of the Korea Association of Health Promotion in Seoul, South Korea, October 23, 2020. REUTERS/Kim Hong-Ji 

A man gets an influenza vaccine at a hospital in Seoul, South Korea, October 21, 2020. REUTERS/Kim Hong-Ji 

A woman gets an influenza vaccine at a hospital in Seoul, South Korea, October 21, 2020. REUTERS/Kim Hong-Ji 

A woman gets an influenza vaccine at a hospital in Seoul, South Korea, October 21, 2020. REUTERS/Kim Hong-Ji 

Doctor Harald Bias looks at the vaccination card of German Health Minister Jens Spahn who receives an influenza injection from at Charite hospital, during the spread of the coronavirus disease (COVID-19), in Berlin, Germany, October 14, 2020. REUTERS/Hannibal Hanschke/Pool 

German Health Minister Jens Spahn shows his vaccination card as he receives an influenza injection at Charite hospital, during the spread of the coronavirus disease (COVID-19), in Berlin, Germany, October 14, 2020. REUTERS/Hannibal Hanschke/Pool 

German Health Minister Jens Spahn receives an influenza injection from doctor Harald Bias at Charite hospital, during the spread of the coronavirus disease (COVID-19), in Berlin, Germany, October 14, 2020. REUTERS/Hannibal Hanschke/Pool 

German Health Minister Jens Spahn receives an influenza injection from doctor Harald Bias at Charite hospital, during the spread of the coronavirus disease (COVID-19), in Berlin, Germany, October 14, 2020. REUTERS/Hannibal Hanschke/Pool REFILE - CORRECTING DATE 

A doctor prepares a syringe to vaccinate a patient as part of the start of the seasonal influenza vaccination campaign in Gouzeaucourt, France, October 13, 2020. REUTERS/Pascal Rossignol 

A doctor vaccinates a patient as part of the start of the seasonal influenza vaccination campaign in Gouzeaucourt, France, October 13, 2020. REUTERS/Pascal Rossignol 

A doctor prepares a syringe to vaccinate a patient as part of the start of the seasonal influenza vaccination campaign in Gouzeaucourt, France, October 13, 2020. REUTERS/Pascal Rossignol 

A doctor vaccinates a patient as part of the start of the seasonal influenza vaccination campaign in Gouzeaucourt, France, October 13, 2020. REUTERS/Pascal Rossignol 

Bavarian Prime Minister Markus Soeder speaks to the media before receiving an influenza injection in Munich, Germany, October 6, 2020. REUTERS/Andreas Gebert 

Bavarian Prime Minister Markus Soeder speaks to the media before receiving an influenza injection in Munich, Germany, October 6, 2020. REUTERS/Andreas Gebert 

Bavarian Prime Minister Markus Soeder receives an influenza injection by Bavarian Health Minister Melanie Huml in Munich, Germany, October 6, 2020. REUTERS/Andreas Gebert 

Bavarian Prime Minister Markus Soeder receives an influenza injection by Bavarian Health Minister Melanie Huml in Munich, Germany, October 6, 2020. REUTERS/Andreas Gebert 

Bavarian Prime Minister Markus Soeder speaks to the media before receiving an influenza injection in Munich, Germany, October 6, 2020. REUTERS/Andreas Gebert 

Bavarian Prime Minister Markus Soeder arrives for an influenza injection in Munich, Germany, October 6, 2020. REUTERS/Andreas Gebert 

Bavarian Prime Minister Markus Soeder receives an influenza injection by Bavarian Health Minister Melanie Huml in Munich, Germany, October 6, 2020. REUTERS/Andreas Gebert 

A healthcare worker holds a jar containing a dose of the flu vaccine during the start of the free influenza vaccination programme, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

A healthcare worker of the free influenza vaccination programme vaccinates a man against the flu, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

Empty jars containing doses of the flu vaccine are pictured inside a bag during the start of the free influenza vaccination programme, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

People line up to receive the vaccine against the flu during the start of the free influenza vaccination programme, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

A healthcare worker holds a jar containing a dose of the flu vaccine during the start of the free influenza vaccination programme, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

Empty jars containing doses of the flu vaccine are pictured inside a bag during the start of the free influenza vaccination programme, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

A healthcare worker of the free influenza vaccination programme vaccinates a man against the flu, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

A healthcare worker of the free influenza vaccination programme vaccinates a man against the flu, as the global spread of the coronavirus disease (COVID-19) continues in Mexico City, Mexico October 1, 2020. REUTERS/Edgard Garrido 

Vienna's Mayor Michael Ludwig arrives to open the free influenza vaccination programme in a tram as the global spread of the coronavirus disease (COVID-19) continues in, Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Vienna's Mayor Michael Ludwig opens the free influenza vaccination programme in a tram as the global spread of the coronavirus disease (COVID-19) continues in, Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Vienna's Mayor Michael Ludwig opens the free influenza vaccination programme in a tram as the global spread of the coronavirus disease (COVID-19) continues in, Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Vienna's Mayor Michael Ludwig and council member Peter Hacker arrive to open the free influenza vaccination programme in a tram as the global spread of the coronavirus disease (COVID-19) continues in, Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Vienna's Mayor Michael Ludwig and council member Peter Hacker open the free influenza vaccination programme in a tram as the global spread of the coronavirus disease (COVID-19) continues in, Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

A healthcare worker of the free influenza vaccination programme holds a flu vaccine inside a tram, as the global spread of the the coronavirus disease (COVID-19) continues, in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

A healthcare worker of the free influenza vaccination programme holds a flu vaccine inside a tram, as the global spread of the the coronavirus disease (COVID-19) continues, in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

A healthcare worker of the free influenza vaccination programme vaccinates a citizen against the flu inside a tram, as the global spread of the the coronavirus disease (COVID-19) continues, in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Healthcare workers of the free influenza vaccination programme vaccinate a citizen against the flu inside a tram, as the global spread of the coronavirus disease (COVID-19) continues in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Healthcare workers of the free influenza vaccination programme wait to vaccinate citizens against the flu as the global spread of the coronavirus disease (COVID-19) continues in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Healthcare workers of the free influenza vaccination programme look outside a tram as they wait to vaccinate citizens against the flu as the global spread of the coronavirus disease (COVID-19) continues in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Healthcare workers of the free influenza vaccination programme disinfect hands inside a tram to vaccinate citizens against the flu as the global spread of the coronavirus disease (COVID-19) continues in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Healthcare workers of the free influenza vaccination programme wait inside a tram to vaccinate citizens against the flu as the global spread of the coronavirus disease (COVID-19) continues in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Healthcare workers of the free influenza vaccination programme wait inside a tram to vaccinate citizens against the flu as the global spread of the coronavirus disease (COVID-19) continues in Vienna, Austria, October 1, 2020. REUTERS/Lisi Niesner 

Republican candidate for the U.S. Congress Rayla Campbell attends a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Three year-old Violet Daniels and her family take part in a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Three year-old Violet Daniels and her family take part in a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Demonstrators attend a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Demonstrators take part in a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Demonstrators attend a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Demonstrators cheer during a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

A man wearing a QAnon vest attends a "No Mandatory Flu Shot Massachusetts" demonstration against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Demonstrators write "No Forced Shots" on the road during a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Sisters Josie and Violet Daniels and their family take part in a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Ashley Makridakis takes part in a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

A demonstrator wears a mask reading "Mask = Psyop" during a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

A demonstrator holds a "Voting Matters" sign during a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

A demonstrator waves his mask in the air instead of wearing it over his nose and mouth during a "No Mandatory Flu Shot Massachusetts" rally against Massachusetts Governor Charlie Baker's order for mandatory influenza vaccinations for all students under the age of 30, an effort to lower the burden on the health care system during the coronavirus disease (COVID-19) outbreak, outside the State House in Boston, Massachusetts, U.S., August 30, 2020. REUTERS/Brian Snyder 

Centers for Disease Control (CDC) Director Robert Redfield explains illness surveillance programs in the United States in front of a chart showing statistics of patients seeking treatment for influenza-like illnesses during the daily coronavirus task force briefing at the White House in Washington, U.S., April 17, 2020. REUTERS/Leah Millis 

A patient suffering influenza symptoms similar to the H1N1 lies on a bed at an intensive care unit of a hospital in Sanaa, Yemen December 23, 2019. REUTERS/Khaled Abdullah 

Nurses attend to a patient suffering influenza symptoms similar to the H1N1 at an intensive care unit of a hospital in Sanaa, Yemen December 23, 2019. REUTERS/Khaled Abdullah