Medical workers and policemen wait for COVID-19 vaccination trials in Colombo, Sri Lanka, Jan. 23, 2021. COVID-19 vaccination trials got underway in Sri Lanka on Saturday, the Health Ministry said, in order to prepare for the vaccination drive once it arrives here next week. (Photo by Ajith Perera/Xinhua)

Medical workers prepare COVID-19 vaccination trials in Colombo, Sri Lanka, Jan. 23, 2021. COVID-19 vaccination trials got underway in Sri Lanka on Saturday, the Health Ministry said, in order to prepare for the vaccination drive once it arrives here next week. (Photo by Ajith Perera/Xinhua)

Medical workers and policemen wait for COVID-19 vaccination trials in Colombo, Sri Lanka, Jan. 23, 2021. COVID-19 vaccination trials got underway in Sri Lanka on Saturday, the Health Ministry said, in order to prepare for the vaccination drive once it arrives here next week. (Photo by Ajith Perera/Xinhua)