Vaccinated California residents can obtain a digital COVID-19 vaccine record here:
https://myvaccinerecord.cdph.ca.gov/
After a Photoshop session making wallet cards for myself and my wife, I tested the QR code. It was unreadable for each of us, on several iOS apps including Camera, and with an online QR-code reader. I've seen one Twitter report with the same experience.
It would make some sense for this to be an intentional security measure, but the FAQ says nothing about this. On the other hand, there are newspaper reports of incomplete issues, but no reporter thought to test the QR-code. One would hope that California tested the software?