Chinese ambassador to Cambodia Wang Wentian, left, presents a box loaded with COVID-19 vaccines to Cambodian Prime Minister Hun Sen during a handover ceremony at Phnom Penh International Airport, in Phnom Penh, Cambodia, Sunday, Feb. 7, 2021. Cambodia on Sunday received its first shipment of COVID-19 vaccine, a donation of 600,000 doses from China, the country's biggest ally. Beijing has been making such donations to several Southeast Asian and African nations in what has been dubbed "vaccine diplomacy," aimed especially at poorer countries like Cambodia. (AP Photo/Heng Sinith)

Workers pull boxes loaded with COVID-19 vaccines before a handing over ceremony at Phnom Penh International Airport, in Phnom Penh, Cambodia, Sunday, Feb. 7, 2021. Cambodia on Sunday received its first shipment of COVID-19 vaccine, a donation of 600,000 doses from China, the country's biggest ally. Beijing has been making such donations to several Southeast Asian and African nations in what has been dubbed "vaccine diplomacy," aimed especially at poorer countries like Cambodia. (AP Photo/Heng Sinith)

Cambodian Prime Minister Hun Sen smiles as his delivers a speech during a handover ceremony at Phnom Penh International Airport, in Phnom Penh, Cambodia, Sunday, Feb. 7, 2021. Cambodia on Sunday received its first shipment of COVID-19 vaccine, a donation of 600,000 doses from China, the country's biggest ally. Beijing has been making such donations to several Southeast Asian and African nations in what has been dubbed "vaccine diplomacy," aimed especially at poorer countries like Cambodia. (AP Photo/Heng Sinith)

Workers pull boxes loaded with COVID-19 vaccines before a handing over ceremony at Phnom Penh International Airport, in Phnom Penh, Cambodia, Sunday, Feb. 7, 2021. Cambodia on Sunday received its first shipment of COVID-19 vaccine, a donation of 600,000 doses from China, the country's biggest ally. Beijing has been making such donations to several Southeast Asian and African nations in what has been dubbed "vaccine diplomacy," aimed especially at poorer countries like Cambodia. (AP Photo/Heng Sinith)

Cambodian Prime Minister Hun Sen, third right, arrives for a handing over ceremony at Phnom Penh International Airport, in Phnom Penh, Cambodia, Sunday, Feb. 7, 2021. Cambodia on Sunday received its first shipment of COVID-19 vaccine, a donation of 600,000 doses from China, the country's biggest ally. Beijing has been making such donations to several Southeast Asian and African nations in what has been dubbed "vaccine diplomacy," aimed especially at poorer countries like Cambodia. (AP Photo/Heng Sinith)

Cambodian Prime Minister Hun Sen gestures during a handover ceremony at Phnom Penh International Airport, in Phnom Penh, Cambodia, Sunday, Feb. 7, 2021. Cambodia on Sunday received its first shipment of COVID-19 vaccine, a donation of 600,000 doses from China, the country's biggest ally. Beijing has been making such donations to several Southeast Asian and African nations in what has been dubbed "vaccine diplomacy," aimed especially at poorer countries like Cambodia. (AP Photo/Heng Sinith)