One would imagine a case where some blood product recipients got sick after a transfusion, and the data would be helpful to narrow down the cause relative to do

One would imagine a case where some blood product recipients got sick after a transfusion, and the data would be helpful to narrow down the cause relative to donor histories. I bet you could encrypt all the histories with a public key however, and only decrypt in such cases: private key held in a safe in the director's office, etc.