(Bloomberg) -- U.K. firms may be allowed to demand proof that customers do not have coronavirus under options being considered to help businesses reopen after the pandemic.

Ministers are conducting a review of whether so-called vaccine passports and test certificates could enable venues to open without fueling a surge in infections once lockdown rules are lifted.

In one potential scenario, someone planning to go to an event could be asked to show staff a medical record on their National Health Service smart-phone app proving they have been vaccinated or tested negative for Covid-19, a person familiar with the matter said.

Prime Minister Boris Johnson has ordered a review of “Covid status certification” to be concluded before June 21, when he wants to fully end restrictions designed to fight the pandemic.

The review is being conducted by officials in the Cabinet Office, led by senior minister Michael Gove. It will also look at implications of vaccine certification for international travelers.

The U.K. wants to use its leadership of the Group of Seven in 2021 to build an international framework for travel, the person said.

Already many governments require evidence of a negative virus tests before they allow travelers to enter their countries. But British officials see moral and ethical issues around forcing people to take tests or have vaccines to go about their daily lives.

The government wants to make sure members of the public are not denied access to key services, the person said. It is unlikely that proof of a vaccine alone will be mandated, but ministers are investigating a combined system that uses vaccine and coronavirus test records together.

“There may well be a role for certification,” Johnson said on Monday. “We just need to get it right.”

Read more: Johnson Says Pandemic End in Sight as He Plans U.K. Recovery

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