2027 ICD-10-CM Diagnosis Code Z28.39Other underimmunization status

ICD-10-CM Codes›Z00–Z99›Z20-Z29›Z28

ICD-10-CM Z28.39
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Z28.39 is a billable ICD-10-CM diagnosis code for other underimmunization status. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 951. The code is not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under No immunization or underimmunization.

Code Identity

ICD-10-CM Code
Z28.39
Billable Status
Yes — Valid for Submission
Code Describes
Other underimmunization status
Short Description
Other underimmunization status
Same as the full description in the CMS dataset.
Parent Code
Z28.3
Underimmunization status

Code Classification

ChapterZ00–Z99Factors influencing health status and contact with health services
SectionZ20-Z29Persons with potential health hazards related to communicable diseases
CategoryZ28Immunization not carried out and underimmunization status
This CodeZ28.39Other underimmunization status

Code EditsBilling

Medicare Code Editor checks that affect claim validity for Z28.39.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Present on Admission (POA)Billing

Z28.39 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Persons with potential health hazards related to communicable diseases (Z20-Z29).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Administration of human anti-D immunoglobulin needed
  • Advised to acquire immunization
  • Advised to acquire influenza immunization
  • Immunization due
  • Immunization overdue
  • Immunization series incomplete
  • Inadequate immune status
  • Influenza vaccination status
  • Influenza vaccine needed
  • Missed childhood immunizations
  • Needs influenza immunization
  • No history of procedure
  • No known immunizations
  • No known procedures
  • No previous immunizations
  • Noncompliance with immunization regimen
  • Not immunized against pertussis
  • Not up to date with immunization due to alternative schedule
  • Not up to date with immunizations
  • Procedure needed
  • Procedure status unknown
  • Requires a cholera booster
  • Requires a course of cholera vaccination
  • Requires a course of gamma globulin
  • Requires a hepatitis A vaccination
  • Requires a meningitis vaccination
  • Requires a tetanus booster
  • Requires a yellow fever vaccination
  • Requires Bacillus Calmette-Guerin vaccination
  • Requires course of hepatitis B vaccination
  • Requires diphtheria, tetanus and pertussis vaccination
  • Requires full course of tetanus vaccination
  • Requires hepatitis B booster
  • Requires influenza virus vaccination
  • Requires measles, mumps and rubella vaccination
  • Requires polio vaccination
  • Requires rabies vaccination course
  • Requires respiratory syncytial virus vaccination
  • Requires rubella vaccination
  • Requires tetanus and diphtheria vaccination
  • Requires typhoid vaccination
  • Requires vaccination
  • Requires vaccination against arthropod-borne viral encephalitis
  • Requires vaccination against cholera with typhoid-paratyphoid
  • Requires vaccination against diphtheria
  • Requires vaccination against diphtheria-tetanus-pertussis with poliomyelitis
  • Requires vaccination against diphtheria-tetanus-pertussis with typhoid-paratyphoid
  • Requires vaccination against leishmaniasis
  • Requires vaccination against measles
  • Requires vaccination against mumps
  • Requires vaccination against pertussis
  • Requires vaccination against plague
  • Requires vaccination against Streptococcus pneumoniae
  • Requires vaccination against tularemia
  • Requires vaccination against typhoid-paratyphoid
  • Requires vaccination against viral hepatitis
  • Requires varicella vaccination
  • Response to immunization
  • Rubella immunization status
  • Rubella virus antibody screening - told non-immune
  • Under immunized
  • Vaccination delayed
  • Vaccination failure
  • Vaccination needed
  • Vaccine product full volume not administered

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Z28.39: its own notes plus those printed at Z28.3, Z28, and Chapter 21. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Z28 Immunization not carried out and underimmunization status applies to 17 codes
  • vaccination not carried out

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Delinquent immunization status
  • Lapsed immunization schedule status

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Z28.3 Underimmunization status applies to 3 codes
  • code, if applicable, to identify:
  • immunization not carried out because of contraindication (Z28.0-)
  • immunization not carried out because of patient decision for other and unspecified reason (Z28.2-)
  • immunization not carried out because of patient decision for reasons of belief or group pressure (Z28.1)
  • immunization not carried out for other reason (Z28.8-)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From Z28 Immunization not carried out and underimmunization status applies to 17 codes
  • if applicable, encounter for immunization safety counseling (Z71.85)

Notes

General instructions on how these codes are used.

From Chapter 21 (Z00-Z99) Factors influencing health status and contact with health services applies to 1,425 codes
  • Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
  • (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
  • (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name Z28.39, its category, or a range that includes it.

Code Also 1

These codes say Z28.39 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • Z71.85 Encounter for immunization safety counseling
    if applicable, immunization not carried out (Z28.-) names Z28.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR FAC017
No immunization or underimmunization
Default principal diagnosis: inpatient No · outpatient No

Code History & ChangesHistory

Replacement Z28.39 replaces the following previously assigned code(s):

  • Z28.3 - Underimmunization status
FY 2023AddedAdded to the ICD-10-CM code setEffective October 1, 2022.
FY 2024–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Z28.39Overview

What is the ICD-10 code for other underimmunization status?

The ICD-10-CM code for other underimmunization status is Z28.39 (sometimes written as Z2839). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is Z28.39 (Underimmunization status) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other underimmunization status on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does Z28.39 group to?

On inpatient claims, other underimmunization status maps to MS-DRG 951 (other Factors Influencing Health Status), which carries a relative weight of 0.5574. Higher weights mean higher Medicare reimbursement.

Can Z28.39 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because other underimmunization status describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

Is Z28.39 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for other underimmunization status on inpatient claims. The code appears in the Persons with potential health hazards related to communicable diseases (Z20-Z29) range of the CMS exempt list.