"Five concrete changes:
- (1)BAA — must have a signed Business Associate Agreement with every vendor in the chain (GCP, model provider). Vertex AI supports BAA.
- (2)PHI handling — all patient data redacted by Cloud DLP before any LLM call. The model never sees raw PHI.
- (3)Encryption — CMEK for data at rest, mTLS for transit, VPC-SC perimeter around the entire system.
- (4)Audit trail — every access to PHI logged with who, when, what, why. Retained 6 years.
- (5)Zero data retention — must confirm model provider doesn't retain prompts/responses for training. Vertex AI ZDR is on by default. I'd also add access reviews every 90 days and annual penetration testing."