WHO has a paper format for a yellow fever card that looks like the following and is used by countries at points of admission.
...
We aren't quite there as far as standardization goes for Covid, but at point:
-- vaccines are more widely available in developing world and other places
-- we know how much it is a "one and done" vaccination vs. one that keeps changing
There definitely could be a similar standardization effort.
....
I have read several articles on the latest attempts to make a digital version of the yellow card for Covid. But I was trying to avoid getting into too much detail, and we are months away from knowing which of the digital efforts will win out in the end. Or how it will work.
I suspect that the digital system will have to obtain information from government databases directly to avoid any chance of user falsified data. But that is only a guess on my part.
This article is non-paywall, I think everyone can read this.
https://www.cnbc.com/2021/03/05/digi...el-abroad.html