2026 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 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Z28.39 is a billable ICD-10-CM diagnosis code for other underimmunization status. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). 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 other POA exempt codes.

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

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Delinquent immunization status
  • Lapsed immunization schedule status

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

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

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 2024–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Z28.39Overview

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, 2025 through September 30, 2026.

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.