A vaccine passport would indicate that they are exempt for unspecified but authenticated reasons.
How do we envision this authentication is done?
I don't mean some fancy QR code smart phone app that's shown where someone scans it with an app it displays a picture of my face with a big green thumbs up.
I mean, how is the authentication done that gets my record into that database? How am I going to prove to that entity that I've been vaccinated?
Once we know that, the next question is, what's the special value I'm getting by having the proof?
Concerts, movie theaters, restaurants?
Visitation to nursing home and long term care facilities?
Crossing state lines? (not likely)
Crossing international borders?
Finally, what's my personal risk for lying and how hard is it for me to lie? Not the risk I cause to others by lying, but the risk to myself.
What's the risk and liability that's taken on by the entity giving me the special treatment if I lie?
All those things have an interaction with each other.
If I'm creating a very small liability for the entity giving me the special treatment by lying, then they don't care that much about how robust my initial proof creating my credential was.
If I'm creating a sizable liability for them, they're going to want robust proof. The credentialing organization could indemnify the group giving me the special treatment. Assuming they're big enough to accept that liability, then only they would care how robust my proof was.
They could force the liability back onto me, but really nobody impacted is going to sue just me. That's a paper risk transfer that falls apart fast.
The CDC card people are getting now, is NOT robust proof of vaccination.