Appearing before the Commons Liaison Committee on Wednesday, the prime minister said the "basic concept of a vaccine certification should not be totally alien to us".
He cited the way surgeons are required to have a Hepatitis B shot to work.
Asked whether ordinary people going to the pub might need a coronavirus jab, Johnson said: "I think that that's the kind of thing that may be up to individual publicans, it may be up to the landlord."
Watch: Boris Johnson says pub landlords could demand COVID certificates
The PM told the committee the public had been "thinking very deeply" about such issues, adding: "My impression is that there is a huge wisdom in the public's feeling about this.
"People, human beings, instinctively recognise when something is dangerous and nasty to them, and they can see that COVID is collectively a threat and they want us as their government and me as the prime minister to take all the actions I can to protect them."
On Thursday Johnson said the result of a review into certificates can be expected by 12 April, but warned it may not be possible to roll them out until everyone has been offered a jab.
He said: “I do think there is going to be a role for certification.
“What we said is we’ll be reporting on the work of the certification group in early April, either on April 5 or April 12.
“There are lots of difficult issues because there are some people who for medical reasons can’t get a vaccination, pregnant women can’t get a vaccination at the moment, you’ve got to be careful about how you do this.
“You might only be able to implement a thorough-going vaccination passport scheme even if you wanted such a thing in the context of when absolutely everybody had been offered a vaccine.”
Last month, when outlining England's "roadmap" out of the coronavirus lockdown, Johnson ruled out any government-led vaccine passport scheme.
"What I don’t think we will have in this country is, as it were, vaccination passports to allow you to go to the pub, or something like that," he said in February.
However, ministers have said some certification might be needed for international travel while considering whether care home staff required shots.
The PM has mandated senior minister Michael Gove to review the role that vaccine certification can have in society, including reopening hospitality venues, saying there were deep and complex ethical issues to explore.
Johnson has also said it is "wholly responsible" for care home companies to consider mandatory vaccinations for staff.
The chief executive of independent care provider Barchester Healthcare Pete Calveley said just 0.1% of potential recruits had declined a job offer since the company imposed its mandatory vaccination policy in mid-January.
He said he hoped the government would make vaccination mandatory for healthcare staff, describing it as a “professional duty”.
When asked about the resumption of international travel, Johnson admitted it was “looking difficult”.
He said: “On April 5, we’ll get the findings of the global travel taskforce and I’ll be setting out what I think may be possible from May 17.
“Things are looking difficult on the continent and we’ll have to look at the situation as it develops.”
Almost 29 million people have received their first vaccine dose in Britain already in the fastest rollout in Europe, and there have been calls to open up the economy faster because of the success of the vaccination programme.
If targets are met, pubs could reopen outside areas on 12 April, and they will then be allowed to welcome guests inside on 17 May before everything opens up fully on 21 June.
Watch: How England will leave lockdown