with US border reopening today, what if foreign travelers use fake vaccination cards? how will airline or border agents tell if the cards are fake or real?

heck, even my US CDC vaccination card looks kind of "fake"...Walgreens pharmacist re-issued me one because I made the stupid mistake of laminating it after 2 doses.... and now the data for all 3 doses are written in the identical handwriting and pen on a new card... looks even more fake because she had absolutely beautiful penwomanship and every character was like artwork...

or is it more like some kind of honor system for foreign traveler attempting to enter the US?