Pfizer-BioNTech coronavirus disease (COVID-19) vaccines are seen at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

A box of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine is seen with a thermometer on top at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

A box of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine is seen at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Walgreens Pharmacists prepare Pfizer-BioNTech coronavirus disease (COVID-19) vaccines at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Walgreens Pharmacists carry Pfizer-BioNTech coronavirus disease (COVID-19) vaccines at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Walgreens Pharmacists prepare Pfizer-BioNTech coronavirus disease (COVID-19) vaccines at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Walgreens Pharmacists prepare Pfizer-BioNTech coronavirus disease (COVID-19) vaccines at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Walgreens Pharmacists carry Pfizer-BioNTech coronavirus disease (COVID-19) vaccines at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

A basket with a protective kit is seen at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

The box of syringes for the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine is seen at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Denise King, a staff member at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Denise Gregory, a staff member at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Denise Gregory, a staff member at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, reacts after receiving the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Staff members at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, prepare to receive the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Ina Siler, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, waits to receive the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

George Valley, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, waits to receive the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

George Valley, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, is given a plant to congratulate him after he received the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

George Valley and Ina Siler, patients at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, wait to receive the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Denise Gregory, Denice King and other staff members at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, talk after receiving the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine, from Walgreens Pharmacist Annette Marshall in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

George Valley, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, gestures after receiving the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. George said: "This is the best thing ever happened. It gives a hope of life and encourages other residents to take it." REUTERS/Yuki Iwamura 

Staff members congratulate Ina Siler, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, after she received the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Ina Siler, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, waits to receive the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Staff members congratulate Ina Siler, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, after she received the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

George Valley, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Denise Gregory, a staff member at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens Pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Ina Siler, a patient at Crown Heights Center for Nursing and Rehabilitation, a nursing home facility, receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Walgreens pharmacist Annette Marshall, in Brooklyn, New York, U.S., December 22, 2020. REUTERS/Yuki Iwamura 

Nurse Jorge Catarino, 35, performs aerobic exercise as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, holds a piece of plastic as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, performs aerobic exercise as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, performs aerobic exercise as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, holds a cube as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, performs aerobic exercise as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

A metronome is pictured during the recovery therapy of the nurse Jorge Catarino, 35, after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, performs aerobic exercise as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, performs aerobic exercise as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, clasps his hands as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

A pulse oximeter is seen placed on the finger of nurse Jorge Catarino, 35, during his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

A nurse checks the blood pressure of nurse Jorge Catarino, 35, during a session of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

Nurse Jorge Catarino, 35, performs aerobic exercise as part of his recovery therapy after suffering from the coronavirus disease (COVID-19) and being intubated for two weeks, at Physical Medicine and Rehabilitation Center of the Mexican Institute of Social Security (IMSS) in Mexico City, Mexico November 30, 2020. REUTERS/Edgard Garrido 

A guest of the day care center of German welfare organisation Caritas follows the instructions of humanoid robot "Pepper" for his rehabilitation work out as the spread of the coronavirus disease (COVID-19) continues in Erlenbach, 50 km south of Frankfurt, Germany, November 25, 2020. Picture taken November 25, 2020. REUTERS/Kai Pfaffenbach 

A guest of the day care center of German welfare organisation Caritas follows the instructions of humanoid robot "Pepper" for his rehabilitation work out as the spread of the coronavirus disease (COVID-19) continues, in Erlenbach, 50 km south of Frankfurt, Germany, November 25, 2020. Picture taken November 25, 2020. REUTERS/Kai Pfaffenbach 

A guest of the day care center of German welfare organisation Caritas follows the instructions of humanoid robot "Pepper" for his rehabilitation workout as the spread of the coronavirus disease (COVID-19) continues, in Erlenbach, 50 km south of Frankfurt, Germany, November 25, 2020, Picture taken November 25, 2020. REUTERS/Kai Pfaffenbach 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

Sonika Randev, who recently completed a physical medicine & rehabilitation residency at Metropolitan Hospital Center in Manhattan, poses for a portrait in the Manhattan borough of New York City, U.S., November 1, 2020. REUTERS/Eduardo Munoz 

A sign stands outside of the Hammonton Center for Rehabilitation and Healthcare one of numerous nursing homes to have staffing shortages during the national outbreak of the coronavirus disease (COVID-19) in Hammonton, New Jersey, U.S., May 19, 2020. Picture taken May 19, 2020. REUTERS/Lucas Jackson 

National Guard soldiers walk in a group outside of the Hammonton Center for Rehabilitation and Healthcare one of numerous nursing homes to have staffing shortages during the national outbreak of the coronavirus disease (COVID-19) in Hammonton, New Jersey, U.S., May 19, 2020. Picture taken May 19, 2020. REUTERS/Lucas Jackson 

Piles of garbage that include personal protective equipment are piled up outside of the Hammonton Center for Rehabilitation and Healthcare one of numerous nursing homes to have staffing shortages during the national outbreak of the coronavirus disease (COVID-19) in Hammonton, New Jersey, U.S., May 19, 2020. Picture taken May 19, 2020. REUTERS/Lucas Jackson 

A United States flag at half-mast is wrapped around a flagpole outside of the Hammonton Center for Rehabilitation and Healthcare one of numerous nursing homes to have staffing shortages during the national outbreak of the coronavirus disease (COVID-19) in Hammonton, New Jersey, U.S., May 19, 2020. Picture taken May 19, 2020. REUTERS/Lucas Jackson 

Employees discard personal protective equipment in a dumpster outside of the Hammonton Center for Rehabilitation and Healthcare one of numerous nursing homes to have staffing shortages during the national outbreak of the coronavirus disease (COVID-19) in Hammonton, New Jersey, U.S., May 19, 2020. Picture taken May 19, 2020. REUTERS/Lucas Jackson 

A path leads through a small courtyard outside of the Hammonton Center for Rehabilitation and Healthcare one of numerous nursing homes to have staffing shortages during the national outbreak of the coronavirus disease (COVID-19) in Hammonton, New Jersey, U.S., May 19, 2020. Picture taken May 19, 2020. REUTERS/Lucas Jackson