ICD-10-CM 2027 diagnosis code
Z28.39Other underimmunization status
Z28.39 is a valid, billable ICD-10-CM code for other underimmunization status. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Looking up by condition? See ICD-10 code for Underimmunization status, ICD-10 code for Delinquent immunization status, ICD-10 code for Lapsed immunization schedule status.
Code last changed in FY2022 (effective October 1, 2021). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About Z28.39
Z28.39 is the ICD-10-CM diagnosis code for other underimmunization status. It belongs to category Z28 (immunization not carried out and underimmunization status), block Z20-Z29 (persons with potential health hazards related to communicable diseases) and chapter 21 (factors influencing health status and contact with health services). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within Z28.3, choose Z28.39 (Other underimmunization status) only when documentation doesn't support a more specific option: underimmunization for COVID-19 status (Z28.31).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 951 (Other Factors Influencing Health Status, relative weight 0.5577), in MDC 23 (Factors Influencing Health Status and Other Contacts with Health Services), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It is not acceptable as the principal diagnosis for an inpatient stay; it may be reported as a secondary diagnosis.
It is exempt from present-on-admission (POA) reporting, so no POA indicator is required.
It was added in FY2022, effective October 1, 2021.
Coding notes
- Delinquent immunization status
- Lapsed immunization schedule status
Notes that apply from higher levels
Instructions written at a parent level also apply to Z28.39.
› From Z28.3 Underimmunization status
- 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-)
› From Z28 Immunization not carried out and underimmunization status
- vaccination not carried out
- , if applicable, encounter for immunization safety counseling (Z71.85)
Broader instructions also apply from Chapter 21: Factors influencing health status and contact with health services.
Alphabetic index entries
6 entriesTerms in the official ICD-10-CM index that lead to Z28.39.
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 23 · Factors Influencing Health Status and Other Contacts with Health Services
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2022 (effective 10/1/2021): Added
- No changes since FY2022.
Common questions about Z28.39
Is Z28.39 billable?
- Yes. Z28.39 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Z28.39 be used as a principal diagnosis?
- No. It is not acceptable as the principal diagnosis for an inpatient stay; it may be reported as a secondary diagnosis.
Is Z28.39 a CC or MCC?
- No. Z28.39 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does Z28.39 group to?
- Z28.39 is used in the MS-DRG v44.0 logic for MS-DRG 951 (Other Factors Influencing Health Status). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.