Digital vaccine passports that show a person has been vaccinated against the coronavirus are being rolled out by governments and businesses worldwide to help restart economies and allow access to events, air travel and even work, but critics warn that they could pose problems from discrimination to theft of health information and fraud.

Airlines and other industry groups are calling on the Biden administration to develop coronavirus health credentials that include information about tests and vaccinations for travelers. The groups argued that the diverse and fragmented approach to digital health credentials that other countries have used for air travel-testing requirements has caused confusion and increased fraud.

Vaccine passports can be put in a smartphone app that links a digital certificate showing a person's vaccination results. There isn't one universal app, but several firms are developing them worldwide.

In the US, IBM and Salesforce are developing a digital health pass that would show if a person has been vaccinated in order to gain access to venues such as workplaces.

Despite the moves to develop some type of proof of vaccination against COVID-19, the WHO warned in January that it isn't known how effective the vaccines are against transmission, which could mean that those who get vaccinated could still pass the coronavirus on to others. And people who have already had the virus may in the future need different vaccine requirements.

"The utility of a vaccine passport is only as good as the evidence of how long the immunity lasts," David Salisbury, an associate fellow at think tank Chatham House, told Bloomberg. "You could find yourself with a stamp in your passport that lasts longer than the antibodies in your blood."