While the United States government has not issued a federal digital vaccine pass, a national standard has nevertheless emerged. To date, 21 states, the District of Columbia and Puerto Rico offer accessibility to the SMART Health Card, a verifiable digital proof of vaccination developed through the Vaccination Credential Initiative (VCI), a global coalition of public and private stakeholders including Microsoft, Salesforce, Oracle, the Mayo Clinic and other health and tech heavyweights.

https://www.forbes.com/sites/suzannerowankelleher/2022/02/24/national-vaccine-quietly-rolled-out/?