epa09586981 A health worker holds a vial of the Pfizer- BioNTech Comirnaty Covid-19 vaccine at a temporary vaccination clinic in Colombo, Sri Lanka, 17 November 2021. Sri Lankan health authorities started to administer the booster dose to senior citizens on 17 November 2021. The country is currently administering Pfizer-BioNTech, Oxford AstraZeneca, China's Sinopharm, Russian Sputnik V, and Moderna vaccines.  EPA/CHAMILA KARUNARATHNE