Originally Posted by
oliver2002
That would explain why a CDC card is no problem

The link supplied also provides indications on how to deal with some of the common problems in getting the pass to work with CDC cards.
It wasn’t too many months ago when the pace of vaccinations for US personnel in Germany was frustratingly slow, but the latest frustration turned to how to get us CDC card users in Europe to be accommodated on the basis of the CDC card. Amusingly, I’m still working out for how to deal with this for my personal purposes without going to Germany to get it done reliably and without any risk of frustration.