Originally Posted by
LBA_flyer
The CDC card is issued by the USA, in the USA for acceptance by the USA for various reasons.
Another issue is that the CDC card is the only universal, authoritative vaccine record that one can carry around on their person. Despite it being more easily forgeable, the USA doesn't have any alternative, as it doesn't have any central vaccination database (it's maintained at the state level), and there is no universal barcode or QR application. For nations where those things do exist, it makes sense to require their use.