Immunization not carried out and underimmunization status (Z28) ICD-10-CM
The Z28 code range covers immunization not carried out and underimmunization status with 23 ICD-10-CM diagnosis codes. 17 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- vaccination not carried out
Code Also
A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
- , if applicable, encounter for immunization safety counseling Z71.85
Codes in the Z28 Range 23 codes · 17 billable
- Z28 Immunization not carried out and underimmunization statusNon-billable
- Z28.0 Immunization not carried out because of contraindicationNon-billable
- 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
- Z28.2 Immunization not carried out because of patient decision for other and unspecified reasonNon-billable
- 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 statusNon-billable
- Z28.31 Underimmunization for COVID-19 statusNon-billable
- Z28.310 Unvaccinated for COVID-19
- Z28.311 Partially vaccinated for COVID-19
- Z28.39 Other underimmunization status
- Z28.8 Immunization not carried out for other reasonNon-billable
- 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
About the Z28 Code Range
The ICD-10 code Z28 and its subcategories are used to document cases where immunization has not been carried out or where underimmunization status applies. These codes cover various reasons for missed vaccines, ranging from medical contraindications to patient or caregiver refusal, as well as other specific circumstances.
The codes under Z28 specify why an immunization was not administered, such as contraindications (Z28.0), patient acute or chronic illness (Z28.01, Z28.02), allergies (Z28.04), or immune compromise (Z28.03). Patient decision–related codes (Z28.1 to Z28.29) include refusal due to beliefs or unspecified reasons, with detailed synonyms clarifying common scenarios like "vaccination declined" or "no consent" for vaccines including tetanus, measles, and COVID-19. The underimmunization status codes (Z28.3 and subcodes) address incomplete immunization series, particularly for COVID-19 vaccines, helping coders identify patients who are unvaccinated or partially vaccinated. Other codes reflect immunization not done due to vaccine unavailability, caregiver refusal, or unspecified reasons, with synonyms like “vaccine product out of stock” or “influenza vaccination not done.” These codes enable precise recording of immunization status, critical for public health tracking and patient care planning.
Questions About This Page
How many billable codes are in the Z28 range?
Of the 23 codes in this range, 17 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the Z28 range classify?
The range classifies immunization not carried out and underimmunization status. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
