Europe plans to launch a digital health pass scheme in June that it hopes will save this summer's holiday season by making it possible for travellers to prove they have been vaccinated against, or tested negative for, COVID-19.
HOW WOULD IT WORK?
The pass, issued by a doctor or health centre, would feature a QR code containing pre-authenticated information that a traveller has been vaccinated against COVID-19 or has received a negative PCR test result.
The QR code, printed out on a piece of paper, would serve as proof of immunity. It would also be possible to scan the code into a smartphone app.
WHO CREATES THE APPS?
The apps are being created by EU member states - France, for example, is already testing its app for airline flights.
In Germany, a team led by IBM is creating one app for users and a second 'checking' app for officials such as airline staff or border guards - a 'green' result means that the health pass is genuine; 'red' means it isn't.
HOW WILL THEY WORK FOR FOREIGN TRAVEL?
The European Commission plans to issue a contract for a central gateway that will make it possible for the various national apps to 'talk' to each other, thus enabling travel between EU countries.
No global standard has yet been agreed, however, meaning that work still needs to be done to deal with overseas visitors.
SOUNDS COMPLICATED - WILL IT WORK?
There are several logistical challenges that still need to be addressed - including how to issue digital health passes to the millions of people in the EU who have already been vaccinated.
One issue still to be resolved is whether antibody tests provide adequate proof that a person who has recovered from COVID-19 is immune, sources say, following cases of reinfection by some variants of the coronavirus.
WHAT ABOUT MY DATA?
Sensitive personal data will typically be stored locally on smartphones in a separate 'wallet', while the EU gateway will only handle the signatures on digital certificates, not the personal data of the holder.
Still, some critics caution that the scheme would be vulnerable to fraud. Others say it would be discriminatory, with only those who can prove that they have been vaccinated enjoying the freedom to travel.