I mean, I guess the Irish government has put more thought into this than I have, and obviously name and dob can narrow things down a bit, like an 18-year-old with a QR code saying they were born in 1950 is going to raise some eyebrows, but it still sort of seems to me like someone who borrowed a QR code from a mate of a similar age would probably be able to get away with it?
90% of adults here are fully vaccinated. And all over 12s...will be fully vacc by end of the month. So I doubt they would need to bother borrowing it.