"Your papers, please". Except it will be a digital app on your smartphone with a QR code and biometric data for positive identification. It will be tied to a master database where all you vaxx certifications will be stored for immediate access. If your screen turns red, you won't get on that airplane, bus, train or get into that restaurant or sport arena. If it turns green, then proceed. Who decides red or green? The WHO, of course.
Source