I cant get my head around how it would work anyway. It might just work for a once in a while event say a concert or similar but not for a daily, weekly, twice a month event like going to the pub or the game. The amount of data that would need to be entered and updated would put any system under huge pressure and mistakes will always be made.
If we cant get track and trace sorted not sure a bigger national system like Covid passport will fare any better.
Projects of this size take years and often fail at the cost of billions with nothing to show for it.
I've heard the travel passport argument but that is supplying data once and it lasts for 10 years so not sure Covid passport is comparable if it needs regularly updating with jabs and test results.
The number of variables is too great not to cause issues. e.g. your age, number of jabs, date of last jab, have you had the latest variant jab, number of tests, date of last test.
The time it takes to update any system with this data could be days which is then too late for you to get into your event or even go to the pub.
How do you correct any data that is wrong. e.g. system says you haven't had both jabs so that's a fail and you don't get let in but you know that you have had both jabs?
And we all know when it comes to sorting out any medical issues or questions you've got no chance of getting an appointment for ages at your doctors so who would administer this whole system/process.
Nightmare!