Boris Johnson said the need for vaccine passports will be reviewed as part the roadmap to ease England's lockdown.
During tonight's Downing Street briefing the Prime Minister was asked a question by ITV's Robert Peston about the role of vaccine passports.
It came after Mr Johnson confirmed on Monday, that a study into the use of vaccine and testing certificates will be one of four reviews conducted as part of easing the current restrictions.
Outlining each review in the House of Commons, Mr Johnson said: "The third review will consider potential role of Covid status certification in helping venues to open safely.
"We are mindful of the many concerns surrounding the exclusion, discrimination and privacy."
Asked by Mr Peston whether he is now persuaded that vaccine passports are "the way to reopen the economy safely", the Prime Minister said other countries will insist on vaccine passports for international travel.
He said: "I think for things like international travel, other countries will unquestionably think of insisting upon them just like you might insist on a certificate that you've had a yellow fever jab.
"So I think that something that's likely to be important in the conversation about international travel."
However, when it comes to travel certificates for domestic travel, Mr Johnson said: "there are some ethical issues, issues about discrimination, to what extent government can compel the use of such certification."
Mr Johnson added: "All that needs to be gone into. At the moment, the emphasis is on vaccinating everybody. That's the non-discriminatory way to go.
"There may be a role for certification. We just need to get it right. Also lateral flow testing - both things together will play an important part."
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The government will set out more on the rules around international travel, mass events and social distancing in the following reviews of the restrictions.
The four reviews, which will include looking at the current social distancing measures and how to increase international travel, are investigating matters upon which ministers do not currently feel they have enough data or information.
The findings of the vaccine passport probe are hoped to be available before stage four of the lockdown easing on June 21 is reached.
Officials have admitted that the review, especially into allowing those who have been vaccinated to have increased rights, poses both moral and ethical questions, as well as practical difficulties.
As well as looking at whether vaccines could enable people to return to a sense of normality, the review will also look at the viability of allowing people to show evidence of a negative test to gain access to a venue.
