Dubai Airports chief executive Paul Griffiths told the BBC: "I don't think there is an alternative."

Critics of the digital systems argue they discriminate against those who cannot get vaccinated.

But Mr Griffiths says he is a complete supporter of the documents, which he says are "inevitable".

"I think the problem is not the vaccine passport and its discrimination. It's the need to roll things out and have a proper globally equitable vaccine programme," he said.

The World Health Organisation and World Travel & Tourism Council are among those opposed to vaccine passports amid fears they will create a "two-tier society".

Last month, Dr Mike Ryan from the WHO repeated concerns about the ethical and fairness issues surrounding vaccine passports.

"They do need to be considered, especially in a world where vaccine is distributed in such a grossly inequitable way," he said.