A container of the active substance needed to make a COVID-19 vaccine is seen at the Mexico City International Airport in Mexico City, Mexico, Feb. 11, 2021. The first shipment of the active substance needed to make a COVID-19 vaccine developed by Chinese pharmaceutical firm CanSino Biologics arrived here on Thursday by air, Mexico's Foreign Affairs Ministry announced. (Photo: Xinhua)

Staff members unload containers of the active substance needed to make a COVID-19 vaccine at the Mexico City International Airport in Mexico City, Mexico, Feb. 11, 2021. The first shipment of the active substance needed to make a COVID-19 vaccine developed by Chinese pharmaceutical firm CanSino Biologics arrived here on Thursday by air, Mexico's Foreign Affairs Ministry announced. (Photo: Xinhua)

Staff members unload containers of the active substance needed to make a COVID-19 vaccine at the Mexico City International Airport in Mexico City, Mexico, Feb. 11, 2021. The first shipment of the active substance needed to make a COVID-19 vaccine developed by Chinese pharmaceutical firm CanSino Biologics arrived here on Thursday by air, Mexico's Foreign Affairs Ministry announced. (Photo: Xinhua)