Proving vaccination status with a "card" would be anyones best bet who is against the jab. That being said; if there is a centralized database being created behind the scenes of those who have actually had the shot is another story. If that's the way they're verifying who is and isn't, then falsifying that information on an official government form could end badly for that individual.
I received my DD3150 yesterday and it's interesting to note that the DoD isn't currently requiring proof of vaccination; just an attestation that you have, haven't or refuse to answer.
It'll be interesting to see if they will require individuals who've been "vaccinated" to show proof (vax card) or is there some type of database the government will tap into to verify ones vaccination status.
I mean if I think about it, the level of effort it would take to prove its validity would be extremely difficult. The only proof of record is that vaccination card thats given to you once you've had the shot. So as long as you print it on some type of card stock, or heavier paper (not printer paper) and find legitimate information of the vaccine type and batch number (which is available on the web) then who's to say if its real or fake? The average person wouldn't be able to tell and if you laminate the card it would be damn near impossible.
I've heard of people downloading and printing a copy of the CDC COVID vaccine card (double sided) and filling it out themselves. There's plenty of pictures on the web of people showing off their filled out vaccine cards. The CDC (according to their website) does not have a vaccination database.
Apparently someone on Reddit made a google doc of the most expensive rugs sold by Brayden Studios and missing children.
https://docs.google.com/spreadsheets/d/18eDoAxvCryW0iWusARvnAGSpcMUM0xniYrHzbW_o6w4/edit#gid=0
Elon spoke on this topic years ago.
https://www.youtube.com/watch?v=Tzb_CSRO-0g