Apple and Google had the (free) solution last April. Authorities are just now getting around to using it.
From Bloomberg's "Los Angeles Vaccine Recipients Can Put the Proof in Apple Wallet" posted Monday:
Covid-19 vaccine recipients in Los Angeles County, a major virus hot spot, will be offered a digital record that will help ensure they get a second shot and could, eventually, be used to gain access to concert venues or airline flights.
The offering is being provided starting this week through a partnership with the startup Healthvana. It’s initially geared toward ensuring people receive both doses of the two-shot regimens that have been authorized in the U.S., including through follow-up notifications before a second appointment.
It will also give recipients a way to verify they have been vaccinated, which they can put into an Apple Wallet or competing Google platform “to prove to airlines, to prove to schools, to prove to whoever needs it,” said Healthvana Chief Executive Officer Ramin Bastani.
My take: I've been wondering when someone would figure this out. You'd think identifying vaccine recipients would be high-priority item.