It came across my mind that the smartphone or other means of proof would have to be constantly updated with “1st Moderna is now 10 months old” and “booster only 4 days ago so not in full effectiveness yet” and more.
Probably added to the misery of noticing you passed the “reply to this offer by....” date for your extra bonus renewal year of Reader’s Digest.
So do the vials of ‘ACME CONvid PREVENTER’ have a “best by” date on them?