A medical staff member receives the first injection with a dose of the Pfizer/BioNTech COVID-19 vaccine, as the coronavirus disease (COVID-19) outbreak continues, in Mexico City, Mexico December 27, 2020.

39-year-old nursing home worker Sanna Elkadiri receives the first Pfizer/BioNTech COVID-19 vaccine in the Netherlands, the last country in the European Union to start vaccinations against the coronavirus disease (COVID-19), in Veghel, Netherlands, January 6, 2021.

Ellen Prosser, known as Nell, who is 100 years old, receives the Oxford/AstraZeneca COVID-19 vaccine from Dr Nikki Kanani at the Sunrise Care Home, amid the coronavirus disease (COVID-19) pandemic in Sidcup, Britain January 7, 2021. Kirsty O'Connor/Pool via REUTERS

One-hundred and one year old Gertrud Haase receives the Pfizer/BioNTech COVID-19 vaccine at the Agaplesion Bethanien Sophienhaus nursing home from vaccinator Fatmir Dalladaku as doctor Irmgard Landgraf looks on in Berlin, Germany December 27, 2020, the day when the country starts its vaccination programme. Kay Nietfeld/Pool via Reuters

A woman receives a COVID-19 vaccine during a vaccination campaign for healthcare professionals over 50 and/or with co-morbidities, at the vaccination centre of Hotel Dieu (Assistance Publique - Hopitaux de Paris) in Paris, France January 4, 2021. Martin Bureau/Pool via REUTERS

Health workers prepare doses of the Pfizer-BioNTech COVID-19 vaccine at a coronavirus disease (COVID-19) vaccination centre in Naples, Italy, January 8, 2021.

A Walgreens Pharmacist prepares the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at Hamilton Park Nursing and Rehabilitation, a nursing home facility, in Brooklyn, New York, U.S., January 4, 2021.

A resident at Hamilton Park Nursing and Rehabilitation, a nursing home facility, receives the coronavirus disease (COVID-19) vaccine from Walgreens Pharmacists in Brooklyn, New York, U.S., January 4, 2020.

Elderly people, who are 65 and over, wait in line at the Department of Health Sarasota COVID-19 vaccination clinic in Sarasota, Florida, U.S. January 4, 2021.

Nurse Sandra Lindsay receives the second dose of a Pfizer coronavirus disease (COVID-19) vaccine, at Long Island Jewish Medical Center in the Queens borough of New York City, U.S., January 4, 2021.

A Florida Department of Health medical worker prepares to administer a COVID-19 vaccine in the parking lot of the Gulf View Square Mall in New Port Richey near Tampa, Florida, U.S. December 31, 2020.

U.S. Vice President-elect Kamala Harris receives a dose of the Moderna COVID-19 vaccine at United Medical Center in Washington, U.S., December 29, 2020.

Daniela Zapata, 42, receives an injection with the Sputnik V (Gam-COVID-Vac) vaccine against the coronavirus disease (COVID-19) at Dr. Pedro Fiorito hospital in Avellaneda, on the outskirts of Buenos Aires, Argentina, December 29, 2020.

Two men wait for their vaccine against the coronavirus disease (COVID-19) at the Treptow Arena vaccination center in Berlin, Germany December 27, 2020. Markus Schreiber/Pool via REUTERS

A health care worker reacts after receiving the Pfizer-BioNTech COVID-19 vaccine as the country begins vaccinations against coronavirus disease, at the Hospital Favoriten in Vienna, Austria December 27, 2020.

Nurse Elena Betti reacts after receiving the Pfizer-BioNTech COVID-19 vaccine against the coronavirus disease at the Careggi hospital in Florence, Italy, December 27, 2020.

A woman receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at Santa Maria hospital in Lisbon, Portugal, December 27, 2020.

Nurses greet soldiers arriving with vials of the Pfizer-BioNTech COVID-19 vaccine against the coronavirus disease in Florence, Italy, December 27, 2020.

Doctor Giovanni Di Perri receives a box with the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at Amedeo di Savoia hospital in Turin, Italy, December 27, 2020.

Michelle Chester, DNP, director, employee health services, Northwell shows the Moderna coronavirus disease (COVID-19) vaccine at Northwell Health's Long Island Jewish Valley Stream hospital in New York, U.S., December 21, 2020.

U.S. Speaker of the House Nancy Pelosi (D-CA) receives the Pfizer-BioNTech COVID-19 vaccine by Dr. Brian Monahan, attending physician of the United States Congress, at the Capitol in Washington, U.S., December 18, 2020. Anna Moneymaker/Pool via REUTERS

Maria Rosaria Capobianchi, one of the first recipients of Pfizer/BioNTech COVID-19 vaccine in Italy, receives her vaccination at the Spallanzani hospital in this screengrab taken from a video, in Rome, Italy December 27, 2020. Ministero della Salute/Handout via REUTERS

Mavis Knox prays next to nurse Sandra Lindsay, before Lindsay receives the second dose of a Pfizer coronavirus disease (COVID-19) vaccine, at Long Island Jewish Medical Center in the Queens borough of New York City, U.S., January 4, 2021.

Brian Pinker, 82, receives the Oxford University/AstraZeneca COVID-19 vaccine from nurse Sam Foster at the Churchill Hospital in Oxford, Britain January 4, 2021. Steve Parsons/Pool via REUTERS

The German armed forces Bundeswehr vaccination team prepares for the Pfizer/BioNTech COVID-19 vaccinations at the Agaplesion Bethanien Sophienhaus nursing home in Berlin, Germany December 27, 2020, the day when the country starts its vaccination programme. Kay Nietfeld/Pool via Reuters

U.S. Vice President Mike Pence receives the COVID-19 vaccine at the White House in Washington, U.S., December 18, 2020.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, prepares to receive his first dose of the new Moderna COVID-19 vaccine at the National Institutes of Health, in Bethesda, U.S., December 22, 2020. Patrick Semansky/Pool via REUTERS

Personal support worker Johanne Lamesse reacts in anticipation to the needle as she receives the Pfizer-BioNTech COVID-19 vaccine at the Civic Hospital in Ottawa, Ontario, Canada December 15, 2020. Adrian Wyld/Pool via REUTERS

Sandra Lindsay, a nurse at Long Island Jewish Medical Center, is inoculated with the coronavirus disease (COVID-19) vaccine by Dr. Michelle Chester from Northwell Health at Long Island Jewish Medical Center in New Hyde Park, New York, U.S., December 14, 2020. Mark Lennihan/Pool via REUTERS

Healthcare workers take part in a rehearsal for the administration of the Pfizer coronavirus disease (COVID-19) vaccine at Indiana University Health in Indianapolis, Indiana, U.S., December 11, 2020.

"Bill" William Shakespeare, 81, receives the Pfizer/BioNTech COVID-19 vaccine at University Hospital, at the start of the largest ever immunisation programme in the British history, in Coventry, Britain December 8, 2020. Britain is the first country in the world to start vaccinating people with the Pfizer/BioNTech jab. Jacob King/Pool via REUTERS TPX IMAGES OF THE DAY

Margaret Keenan, 90, is applauded by staff as she returns to her ward after becoming the first person in Britain to receive the Pfizer/BioNTech COVID-19 vaccine at University Hospital, at the start of the largest ever immunisation programme in the British history, in Coventry, Britain December 8, 2020. Britain is the first country in the world to start vaccinating people with the Pfizer/BioNTech jab. Jacob King/Pool via REUTERS