A Palestinian man receives a dose of COVID-19 vaccine at a medical center during a vaccination campaign in Gaza city, on April 20, 2021. (Photos: Rizek Abdeljawad/Xinhua)

A Palestinian woman receives a dose of COVID-19 vaccine at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.

A Palestinian woman receives a dose of COVID-19 vaccine at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.

A health worker prepares a dose of COVID-19 vaccine at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.

Palestinians wait to receive COVID-19 vaccines at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.

A Palestinian man receives a dose of COVID-19 vaccine at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.

Palestinians wait to receive COVID-19 vaccines at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.

A Palestinian man receives a dose of COVID-19 vaccine at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.

A Palestinian man receives a dose of COVID-19 vaccine at a medical center during a vaccination campaign in Gaza city, on April 20, 2021.