It may only be possible to implement a vaccine passports scheme once everybody has been offered a jab, Boris Johnson has suggested.
The prime minister said a review on their use would report in April but no decisions have been taken.
He said there were “lots of difficult issues… moral complexities, ethical problems that need to be addressed”.
It comes as publicans cast doubt on Mr Johnson’s suggestion pub-goers might have to prove their vaccination status.
Speaking on a visit to a nursery in West London, Mr Johnson said: “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.”
Mr Johnson said previous coronavirus infections could be a feature used if Covid-19 health certificates are adopted.
“There are three basic components. There’s the vaccine, there’s your immunity you might have had after you’ve had Covid, and there’s testing – they are three things that could work together.
However he added: “No decisions have been taken at all. One thing I will make clear is none of this is obviously going to apply on April 12 when it will all be outdoors anyway.”
A Downing Street source earlier said the review would include looking at how people’s vaccination and testing status could be stored securely and displayed on a mobile phone, and the circumstances under which such a system could apply.
MPs will vote later on new coronavirus laws for England’s roadmap out of lockdown.
They will also be asked to approve the government’s plan to renew emergency coronavirus powers for another six months. The Coronavirus Act was introduced in March 2020 at the start of the pandemic.
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