Tech-savvy Estonia has developed an app that could serve as a kind of digital "immunity passport", allowing users with antibodies to show employers and others their reduced risk of spreading the coronavirus.
The Baltic state is not the only country exploring the potential of such a passport, though global health authorities and experts urge caution, given concerns over the accuracy of antibody tests.
The Immuunsuspass (ImmunityPassport) app, which is being tested out this month, was developed by the Estonian tech firms Transferwise and Guardtime in cooperation with health specialists for the Back to Work non-governmental organisation.
"The app we've created can provide necessary data to schools and employers to help them make decisions," TransferWise cofounder Taavet Hinrikus told AFP.
"However, before it's adopted for widespread use, we need to achieve a scientific consensus on COVID-19 immunity."
The app allows users to access their COVID-19 test results for an hour after proving their identity. They can also share the results with others using a QR-code that expires after a minute.
The developers say this ensures that the immunity results are up-to-date and protected against unauthorised sharing.
In the future, users will also be able to access their vaccination data.
The World Health Organization issued a warning in late April that there was "not enough evidence" to give people "risk-free certificates," but hours later appeared to backpedal with a modified statement.
In the follow-up, WHO said it expected that people who are infected with COVID-19 "will develop an antibody response that will provide some level of protection" but added that "what we don't yet know is the level of protection or how long it will last".
Estonia -- or E-stonia as it is sometimes dubbed -- has made a name for itself as a trailblazer in technology over the years. It notably pioneered e-voting in 2005 and plays host to NATO's elite cyber defence centre.