Z28.81
BillableImmunization not carried out due to patient having had the disease
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Z28.81 an HCC code?
No. Z28.81 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
Z28.81 is the ICD-10-CM diagnosis code for immunization not carried out due to patient having had the disease. A patient did not receive a vaccine because they have already had the disease that the vaccine prevents. Z28.81 sits in the ICD-10-CM chapter for factors influencing health status and contact with health services (z00-z99), within the section covering persons with potential health hazards related to communicable diseases (z20-z29).
Z28.81 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Document evidence of prior disease (clinical diagnosis, serology, or medical history).
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Z28.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document evidence of prior disease (clinical diagnosis, serology, or medical history)
- •This is appropriate for diseases like chickenpox or measles where natural immunity is documented