How long will my biometric information be stored?

Unless otherwise required by law, the personal information (including your fingerprint image and template) collected using biometrics is retained on behalf of the USMLE program sponsors in a secure, centralized database in the United States on test day and for a period of 5 years from the date of your most recent testing appointment with Prometric.

Source: http://usmleworldwide.com/blog/?p=112