Call me crazy, but ...

[Стефан Васильев]

if a person, within the EU, would put his COVID vaccination certificate 
QR-Code
in his pub-key as photo-ID I would say that than another GnuPG user, 
within
the EU, or maybe later in the U.S. and elsewhere too, would have the 
assurance,
without that the public key is otherwise signed, that this pub key 
belongs to that
person.

On GitHub is a decoder available, which allows users to verify the 
digital signature
of such COVID certs, with trustlists from EU member states.

https://github.com/stapelberg/coronaqr

Regards
Stefan