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, US, Dec 16, 2020. [Photo/Agencies]

The Moderna coronavirus disease (COVID-19) vaccine is displayed at Northwell Health's Long Island Jewish Valley Stream hospital in New York, US, Dec 21, 2020. [Photo/Agencies]

Leonida Lipshy, RN in the COVID unit at the Broward Health Medical Center, gives Dr. Greg Dubrovich, D.O., Emergency Department at Broward Health Imperial Point, a shot of the Moderna COVID-19 vaccine on Dec 23, 2020 in Fort Lauderdale, Florida. Broward Health Medical Center began vaccinating frontline healthcare workers last week with the Pfizer-BioNtech COVID-19 vaccine and are continuing to inoculate frontline caregivers with both of the vaccines after the arrival of the Moderna. [Photo/Agencies]