Digital vaccine credentials can confirm that a person has been vaccinated or tested negative for COVID-19. They can be a tool to reduce the disease's spread, and allow travel and other activities to resume safely. Users of such credentials can provide their COVID-19 information on a mobile device through a secure, digital code for fast and contactless scanning. Airports and other venues could process larger numbers of people more quickly with these credentials than with paper vaccine cards. However, challenges that may limit the use of these credentials include concerns about the security and privacy of users' health data.