Travellers line up for immigration procedures at an airport before entering Vietnam. (Photo: VNA)

Tran Dac Phu, senior advisor at the Health Ministry, said the world has a tradition of certifying travel for those who have been fully vaccinated against a number of diseases such as cholera, lymphadenitis and yellow fever. However, COVID-19 is a new infectious disease, requiring newly developed vaccines.

As COVID-19 vaccines have received emergency approval, a number of matters have remained unclear and some vaccines may be less effective against emerging variants, Mr. Phu said, adding there are also risks from counterfeit “vaccine passports”.

His comments came as countries like China and Israel started issuing digital health certificates for travelers who had been vaccinated against COVID-19, also dubbed "vaccine passports."