The Prime Minister told MPs people visiting pubs could be asked to provide a vaccine certificate but it "may be up to individual publicans".
Reporting on the BBC said a review is looking into whether people should have to prove they have been vaccinated, as lockdown measures ease. A government source said the option of allowing people to show a negative test was also being looked at.
The idea of asking pub goers to show a vaccine certificate was raised at Wednesday's House of Commons Liaison Committee hearing, when Conservative William Wragg asked Mr Johnson if vaccine certificates were "compatible with a free society such as ours".
Mr Wragg then asked, what about "ordinary citizens going to the pub?" and the prime minister replied: "That's the kind of thing that may be up to individual publicans."
Pushed further, Mr Johnson said: "I find myself in this long national conversation thinking very deeply about it" adding that the public "want me as prime minister to take all the action I can to protect them".
Mr Johnson also said it seemed "wholly responsible" for care companies to require their workers to be vaccinated and "the principle is there" in terms of professions requiring certain vaccines when "entrusted with care of a patient".