Justin Sambol, right, Senior Associate Dean for Clinical Affairs, receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Ambulatory Care Technician Sady Ferguson, at Rutgers New Jersey Medical School for COVID-19 at University Hospital in Newark, New Jersey, U.S., December 15, 2020. Kirsten Luce/Pool via REUTERS

U.S. Navy Command Master Chief Randy F. Swanson receives a Pfizer COVID-19 vaccination at Walter Reed National Military Medical Center at in Bethesda, Maryland, U.S. December 14, 2020. Picture taken December 14, 2020. U.S. Navy/Mass Communication Specialist 2nd Class Kurtis A. Hatcher/Handout via REUTERS

Physician Joyce Limurti, 40, flexes her bicep as she is given the coronavirus disease (COVID-19) vaccine at Dignity Health Glendale Memorial Hospital and Health Center in Glendale, California, U.S., December 17, 2020.

Physician Emily Ryan, 40, poses for a photo with a Dr. Fauci hoodie after having the coronavirus disease (COVID-19) vaccine at Dignity Health Glendale Memorial Hospital and Health Center in Glendale, California, U.S., December 17, 2020.

Health and Human Services Secretary Alex Azar asks Dr. Raymond Pla, an anesthesiologist at George Washington University Hospital, if his vaccination for COVID-19 hurt, in Washington, D.C., U.S. December 14, 2020. "Not at all," answered Pla. Jacquelyn Martin/Pool via REUTERS

Dr. Tommy Wong holds up his vaccination record as he waits after he received one of the first vaccinations at Mt. Sinai Hospital from Pfizer-BioNTech, during the coronavirus disease (COVID-19) pandemic in the Manhattan borough of New York City, New York, U.S., December 15, 2020.

Richard Guarino BMC Supply Chain Operations Associate Director delivers Pfizer's coronavirus disease (COVID-19) vaccine to the pharmacy at Boston Medical Center in Boston, Massachusetts, U.S. December 14, 2020. Jessica Rinaldi/POOL via REUTERS

New Jersey Governor Phil Murphy, watches as Maritza Beniquez, RN, reacts to receiving the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from Ambulatory Care Technician Sady Ferguson at Rutgers New Jersey Medical School for COVID-19 at University Hospital in Newark, New Jersey, U.S., December 15, 2020. Kirsten Luce/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. Sheetal Sheth, an OB-GYN and Medical Director for Labor and Delivery at George Washington University Hospital, is vaccinated for COVID-19 by nurse Lillian Wirpsza in Washington, D.C., U.S. December 14, 2020. Jacquelyn Martin/Pool via REUTERS

Health workers listen to New Jersey Governor Phil Murphy speaking to the media after attending a tour at University Hospital's COVID-19 vaccine clinic at Rutgers New Jersey Medical School in Newark, New Jersey, U.S., December 15, 2020.

Dr. Karim Yatim receives the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at Brigham and Women's Hospital in Boston, Massachusetts, U.S., December 16, 2020.

U.S. Surgeon General Jerome Adams gives the thumbs up as he receives the coronavirus disease (COVID-19) vaccine at the White House in Washington, U.S., December 18, 2020.

Registered nurse Nikki Galanakis, 28, is given the coronavirus disease (COVID-19) vaccine at Martin Luther King Jr. Community Hospital, in South Los Angeles, California, U.S., December 17, 2020.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, elbow bumps U.S. Vice President Mike Pence, at an event where Pence received the coronavirus disease (COVID-19) vaccine at the White House in Washington, U.S., December 18, 2020.

Cheryl Tull (L), Associate Chief Nursing Officer at Boston Medical Center, receives a coronavirus disease (COVID-19) vaccine administered by LPN Eunide Guillet at Boston Medical Center in Boston, Massachusetts, U.S., December 16, 2020. Erin Clark/Pool via REUTERS

Doses of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine are taken out of refrigeration to be administered at Brigham and Women's Hospital in Boston, Massachusetts, U.S., December 16, 2020.

Acting U.S. Defense Secretary Christopher Miller, gets his first shot of the Pfizer-BioNTech COVID-19 vaccine, administered by HN Samantha Alvarez, at the Walter Reed National Military Medical Center in Bethesda, Maryland, U.S., December 14, 2020. Manuel Balce Ceneta/Pool via REUTERS

Gov. Gavin Newsom holds up a vial of the Pfizer-BioNTech COVID-19 vaccine at Kaiser Permanente Los Angeles Medical Center in Los Angeles, California, U.S. December 14, 2020. Jae C. Hong/Pool via REUTERS

Medical staff administers the Pfizer-BioNTech COVID-19 Vaccine at Jackson Memorial Hospital in Miami, Florida, U.S., December 15, 2020.

Physician Alister Martin receives one of the first doses of the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine from RN Jennifer Lisciotti at Massachusetts General Hospital in Boston, Massachusetts, U.S., December 16, 2020. Craig F. Walker/Pool via REUTERS

Medical staff prepare to administer and receive the Pfizer-BioNTech COVID-19 Vaccine at Jackson Memorial Hospital in Miami, Florida, U.S., December 15, 2020.