A medical worker (L) receives a COVID-19 vaccine at the General Hospital in Mexico City, Mexico, on Dec. 24, 2020. Mexico on Thursday kicked off its vaccination campaign against the COVID-19, with a vaccine developed by U.S. laboratory Pfizer and its German partner BioNTech. (Photo by Luis Licona/Xinhua)

Maria Irene Ramirez (2nd R), head of nursing at the intensive care unit of the Ruben Lenero Hospital in Mexico City, receives the first COVID-19 vaccine at the General Hospital in Mexico City, Mexico, on Dec. 24, 2020. Mexico on Thursday kicked off its vaccination campaign against the COVID-19, with a vaccine developed by U.S. laboratory Pfizer and its German partner BioNTech. (Photo by Luis Licona/Xinhua)

Maria Irene Ramirez (R), head of nursing at the intensive care unit of the Ruben Lenero Hospital in Mexico City, receives the first COVID-19 vaccine at the General Hospital in Mexico City, Mexico, on Dec. 24, 2020. Mexico on Thursday kicked off its vaccination campaign against the COVID-19, with a vaccine developed by U.S. laboratory Pfizer and its German partner BioNTech. (Photo by Luis Licona/Xinhua)

Mexican Deputy Health Minister Hugo Lopez-Gatell speaks during the launch of the vaccination campaign at the General Hospital in Mexico City, Mexico, on Dec. 24, 2020. Mexico on Thursday kicked off its vaccination campaign against the COVID-19, with a vaccine developed by U.S. laboratory Pfizer and its German partner BioNTech. (Photo by Luis Licona/Xinhua)

A medical worker (L) receives a COVID-19 vaccine at the General Hospital in Mexico City, Mexico, on Dec. 24, 2020. Mexico on Thursday kicked off its vaccination campaign against the COVID-19, with a vaccine developed by U.S. laboratory Pfizer and its German partner BioNTech. (Photo by Luis Licona/Xinhua)

A medical worker (C) receives a COVID-19 vaccine at the General Hospital in Mexico City, Mexico, on Dec. 24, 2020. Mexico on Thursday kicked off its vaccination campaign against the COVID-19, with a vaccine developed by U.S. laboratory Pfizer and its German partner BioNTech. (Photo by Luis Licona/Xinhua)

A medical worker (R) receives a COVID-19 vaccine at the General Hospital in Mexico City, Mexico, on Dec. 24, 2020. Mexico on Thursday kicked off its vaccination campaign against the COVID-19, with a vaccine developed by U.S. laboratory Pfizer and its German partner BioNTech. (Photo by Luis Licona/Xinhua)