2027 ICD-10-CM Diagnosis Code Z28Immunization not carried out and underimmunization status

ICD-10-CM Codes›Z00–Z99›Z20-Z29›Z28

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

Z28 is a non-billable ICD-10-CM category code for immunization not carried out and underimmunization status, so it cannot be submitted on claims. Use a more specific code from this category instead, such as Z28.01, Z28.02, Z28.03, and Z28.04.

Code Identity

ICD-10-CM Code
Z28
Billable Status
No — Non-Billable Category
Code Describes
Immunization not carried out and underimmunization status
Short Description
Immunization not carried out and underimmunization status
Same as the full description in the CMS dataset.
Chapter
Z20-Z29
Persons with potential health hazards related to communicable diseases

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 CodeZ28Immunization not carried out and underimmunization status

Specific Coding for Immunization not carried out and underimmunization statusOverview

Non-specific codes like Z28 require more characters. Use one of these billable codes instead:

  • Z28.0 for Immunization not carried out because of contraindication

  • Use Z28.01 for Immunization not carried out because of acute illness of patient

  • Use Z28.02 for Immunization not carried out because of chronic illness or condition of patient

  • Use Z28.03 for Immunization not carried out because of immune compromised state of patient

  • Use Z28.04 for Immunization not carried out because of patient allergy to vaccine or component

  • Use Z28.09 for Immunization not carried out because of other contraindication

  • Use Z28.1 for Immunization not carried out because of patient decision for reasons of belief or group pressure

  • Z28.2 for Immunization not carried out because of patient decision for other and unspecified reason

  • Use Z28.20 for Immunization not carried out because of patient decision for unspecified reason

  • Use Z28.21 for Immunization not carried out because of patient refusal

  • Use Z28.29 for Immunization not carried out because of patient decision for other reason

  • Z28.3 for Underimmunization status

  • Z28.31 for Underimmunization for COVID-19 status

  • Use Z28.39 for Other underimmunization status

  • Z28.8 for Immunization not carried out for other reason

  • Use Z28.81 for Immunization not carried out due to patient having had the disease

  • Use Z28.82 for Immunization not carried out because of caregiver refusal

  • Use Z28.83 for Immunization not carried out due to unavailability of vaccine

  • Use Z28.89 for Immunization not carried out for other reason

  • Use Z28.9 for Immunization not carried out for unspecified reason

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Z28: its own notes plus those printed at 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.

  • vaccination not carried out

Code Also

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

  • 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, its category, or a range that includes it.

Code Also 1

These codes say Z28 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.-)

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Z28Overview

What is the ICD-10 code for immunization not carried out and underimmunization status?

Z28 is the ICD-10-CM category for immunization not carried out and underimmunization status, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is Z28 (Immunization not carried out and underimmunization status) a billable code?

No. This is a category header that groups the codes for immunization not carried out and underimmunization status, and headers cannot be submitted on claims. Claims for immunization not carried out and underimmunization status need a more specific code from this category, such as Z28.01, Z28.02, and Z28.03.