A look at the SMART Health Card, a minimal verification system that uses QR codes to check COVID-19 vaccine status, available to ~200M people in the US (David Ingram/NBC News)

David Ingram / NBC News: A look at the SMART Health Card, a minimal verification system that uses QR codes to check COVID-19 vaccine status, available to ~200M people in the US  —  The SMART Health Card is voluntary and minimal by design to protect personal information.  About 80 percent […]