Health workers wait in line to receive Sinovac COVID-19 vaccine from China during a mass vaccination program with health workers as a main priority group in Surabaya, Indonesia, Jan. 31, 2021. (Photo by Kurniawan/Xinhua)

A member of medical staff prepares a dose of Sinovac COVID-19 vaccine from China during a mass vaccination program with health workers as a main priority group in Surabaya, Indonesia, Jan. 31, 2021. (Photo by Aditya Hendra/Xinhua)

A health worker takes a selfie when receiving a dose of Sinovac COVID-19 vaccine from China during a mass vaccination program with health workers as a main priority group in Surabaya, Indonesia, Jan. 31, 2021. (Photo by Kurniawan/Xinhua)

A health worker (L) receives a dose of Sinovac COVID-19 vaccine from China during a mass vaccination program with health workers as a main priority group in Surabaya, Indonesia, Jan. 31, 2021. (Photo by Aditya Hendra/Xinhua)