Integrating with vaccine registries is another unique beast, and we haven't had the pleasure of doing that yet. Each state has actually has its own registry, they don't even use FHIR, and instead use an even older standard than C-CDAs - CAIR2 HL7v2: https://www.cdph.ca.gov/Programs/CID/DCDC/CAIR/CDPH%20Docume...
We don't support this yet - but we'll get there.
https://repository.immregistries.org/resource/hl7-version-2-...
The CDC IZ Gateway can make it somewhat easier to work with multiple state registries.
https://www.cdc.gov/vaccines/programs/iis/iz-gateway/overvie...
In practice the C-CDAs obtained from providers sometimes include immunization section entries so you can pick up some records that way as well
Didn't know CAIR2 was only used in CA - I guess a correct statement would be every state has an offshoot of HL7v2, with CAIR2 being one of them, as you mentioned.
> In practice the C-CDAs obtained from providers sometimes include immunization section entries
Yes for sure - we get a lot of those from C-CDAs already, these registries would be just another way to make the data even more authoritative/accurate.