states' responses have ranged from NY already having a system rolled out and in use that they hope to become the national standard to FL gov issuing an EO prohibiting them
As Sal posted last night, MO is working on prohibiting requiring vaccine credentials for travel as part of a broader transportation bill
even the ACLU isn't much help
https://www.aclu.org/news/privacy-technology/theres-a-lot-that-can-go-wrong-with-vaccine-passports/