Z28.39 ICD-10-CM Code: Other underimmunization status

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Z28.39 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on Z28.39 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for Z28.39

MedCoder structured workflow — derived from this code’s own official record

Before you code Z28.39

1. “Other” (NEC) means the condition is specified in the record but no dedicated code captures it. Confirm the documented form is not one a sibling code names before settling on Z28.39; if the record states no specifics at all, the unspecified sibling applies instead. “Other” codes are for documented conditions the classification gives no specific code; “unspecified” codes are for records lacking the detail (Guidelines I.A.9.a, I.A.9.b).

   ReviewZ28.31

   See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

2. Confirm the reason for the encounter this Z code records: the circumstance it records. Check whether the code may be reported as first-listed or principal — some Z codes are limited to one position — and do not report a history or status code for a condition documented as current. Z code categories and their reporting positions (Guidelines I.C.21.c, I.C.21.c.15).

   Guide: Z codes as principal or first-listed diagnosis →

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

The conditions the Use Additional Code note names

Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.

The reason for the encounter

Whether the code records the encounter’s purpose, a status, or a history — and whether it may be first-listed (Guidelines I.C.21.c).

Any detail beyond this code’s title

What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

• Use Additional Code — after identifying Z28.39(5 notes)

  Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with Z28.39 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

  ReviewZ28.0, Z28.2, Z28.1, Z28.8

  See the official tabular notes · Guidelines I.A.13

• Code Also — related condition(1 note)

  Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

  ReviewZ71.85

  See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Indexed Clinical Terms (6)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

• Delinquent immunization status
• Lapsed immunization schedule status
• Status (post), delinquent immunization
• Status (post), lapsed immunization schedule
• Status (post), underimmunization
• Underimmunization status

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Verify Before Coding

• Principal-diagnosis restriction. The Medicare Code Editor lists this code as unacceptable as a principal diagnosis: it describes a circumstance influencing health status rather than a current illness or injury being treated. It is valid as a secondary diagnosis.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name Z28.39 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Code Also instruction: Z71.85 — Encounter for immunization safety counseling (via Z28.-).

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 1 MS-DRG: DRG 951 (MDC 23).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):FAC017 — No immunization or underimmunization.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Principal diagnosis restriction (Medicare Code Editor)

Not acceptable as a principal diagnosis on an inpatient claim.

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (No immunization or underimmunization).

Z28.01 — Immunization not carried out because of acute illness of patient, Z28.02 — Immunization not carried out because of chronic illness or condition of patient, Z28.03 — Immunization not carried out because of immune compromised state of patient, Z28.04 — Immunization not carried out because of patient allergy to vaccine or component, Z28.09 — Immunization not carried out because of other contraindication, Z28.1 — Immunization not carried out because of patient decision for reasons of belief or group pressure, Z28.20 — Immunization not carried out because of patient decision for unspecified reason, Z28.21 — Immunization not carried out because of patient refusal, Z28.29 — Immunization not carried out because of patient decision for other reason, Z28.3 — Underimmunization status, Z28.310 — Unvaccinated for COVID-19, Z28.311 — Partially vaccinated for COVID-19, Z28.81 — Immunization not carried out due to patient having had the disease, Z28.82 — Immunization not carried out because of caregiver refusal, Z28.83 — Immunization not carried out due to unavailability of vaccine, Z28.89 — Immunization not carried out for other reason, Z28.9 — Immunization not carried out for unspecified reason

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Status”; these codes share that main term but sit in a different category of the Tabular List.

Z17.22 — Progesterone receptor negative status (progesterone receptor, negative), Z17.31 — Human epidermal growth factor receptor 2 positive status (human epidermal growth factor 2 receptor, positive), Z17.32 — Human epidermal growth factor receptor 2 negative status (human epidermal growth factor 2 receptor, negative), Z17.410 — Hormone receptor positive with human epidermal growth factor receptor 2 positive status (combined receptor, positive, hormone receptor positive with human epidermal growth factor receptor 2 positive), Z17.411 — Hormone receptor positive with human epidermal growth factor receptor 2 negative status (combined receptor, positive, hormone receptor positive with human epidermal growth factor receptor 2 negative), Z17.420 — Hormone receptor negative with human epidermal growth factor receptor 2 positive status (combined receptor, negative, hormone receptor negative with human epidermal growth factor receptor 2 positive), Z17.421 — Hormone receptor negative with human epidermal growth factor receptor 2 negative status (combined receptor, negative, hormone receptor negative with human epidermal growth factor receptor 2 negative), Z19.1 — Hormone sensitive malignancy status (malignancy, hormone sensitive), Z19.2 — Hormone resistant malignancy status (malignancy, hormone resistant), Z21 — Asymptomatic human immunodeficiency virus [HIV] infection status (human immunodeficiency virusinfection, asymptomatic), Z33.1 — Pregnant state, incidental (pregnancy, incidental), Z39.0 — Encounter for care and examination of mother immediately after delivery (postpartum, care immediately after delivery), Z39.2 — Encounter for routine postpartum follow-up (postpartum), Z56.82 — Military deployment status (deployment), Z66 — Do not resuscitate (do not resuscitate), Z74.01 — Bed confinement status (bed confinement), Z76.82 — Awaiting organ transplant status (awaiting organ transplant), Z78.1 — Physical restraint status (physical restraint), Z87.890 — Personal history of sex reassignment (sex reassignment surgery status), Z90.02 — Acquired absence of larynx (laryngectomy), +77 more

Contextual Map

Every relationship of Z28.39 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run Z28.39 with this related code in Claim Check

Hierarchy

• Z00-Z99 — Chapter 21: Factors Influencing Health Status and Contact with Health Services (Z00-Z99) (Z00-Z99)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z20-Z29 — Persons with potential health hazards related to communicable diseases[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Code Also instructions

• Z71.85 — Encounter for immunization safety counseling[Code Also](via Z28.-): “, if applicable, immunization not carried out (Z28.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• FAC017 — No immunization or underimmunization[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

MS-DRG Grouper

• DRG 951 — OTHER FACTORS INFLUENCING HEALTH STATUS[MS-DRG]: “OTHER FACTORS INFLUENCING HEALTH STATUS (MDC 23)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 23 — Factors Influencing Health Status and Other Contacts with Health Services[MDC crossing]: “Factors Influencing Health Status and Other Contacts with Health Services — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 1,235 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

• Delinquent immunization status[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Lapsed immunization schedule status[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Status (post), delinquent immunization[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Status (post), lapsed immunization schedule[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Status (post), underimmunization[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Underimmunization status[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (22)

• Z28 — Immunization not carried out and underimmunization status[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z28.0 — Immunization not carried out because of contraindication[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z28.01 — Immunization not carried out because of acute illness of patient[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z28.02 — Immunization not carried out because of chronic illness or condition of patient[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z28.03 — Immunization not carried out because of immune compromised state of patient[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z28.04 — Immunization not carried out because of patient allergy to vaccine or component[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z28.09 — Immunization not carried out because of other contraindication[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Z28.1 — Immunization not carried out because of patient decision for reasons of belief or group pressure[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 14 more

Change history

• FY2022 — Added to the code set[Change history]— CMS release files (code change ledger) · icd10cm-fy2022

Relevant guides

• How Do I Code a Flu Shot or Other Immunization Visit? Z23 for the Encounter, Z28 When the Vaccine Is Not Given, Z28.3 for Underimmunization Status →

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Coding guidelines Official source data

ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Inpatient payment groups Official source data

CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Z28.39 in its code family, with their registry titles.

• Z28.29 — Immunization not carried out because of patient decision for other reason
• Z28.3 — Underimmunization status
• Z28.31 — Underimmunization for COVID-19 status
• Z28.310 — Unvaccinated for COVID-19
• Z28.311 — Partially vaccinated for COVID-19
• Z28.8 — Immunization not carried out for other reason
• Z28.81 — Immunization not carried out due to patient having had the disease
• Z28.82 — Immunization not carried out because of caregiver refusal
• Z28.83 — Immunization not carried out due to unavailability of vaccine
• Z28.89 — Immunization not carried out for other reason

View all codes in the Z28 family