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ICD-10-CM 2027 diagnosis code

Z28.31Underimmunization for COVID-19 status

Not billable — use a more specific code

Z28.31 is a header code, so it can't be reported by itself. Choose one of the 2 more specific codes beneath it.

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 Z28.31

Z28.31 is the ICD-10-CM diagnosis code for underimmunization for COVID-19 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 a header code, so it can't be reported by itself; one of its 2 subcodes must be used instead.

Within Z28.3 (underimmunization status), Z28.31 is specifically for underimmunization for COVID-19 status. Related codes cover other underimmunization status (Z28.39).

To report this condition, pick the subcode that matches the documentation: Z28.310 (COVID-19) and Z28.311 (COVID-19).

It was added in FY2022, effective October 1, 2021.

Specific codes under Z28.31

Coding notes

Note
  • These codes should not be used for individuals who are not eligible for the COVID-19 vaccines, as determined by the healthcare provider.

Notes that apply from higher levels

Instructions written at a parent level also apply to Z28.31.

› From Z28.3 Underimmunization status
Use additional code
  • 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
Includes
  • vaccination not carried out
Code also
  • , 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

4 entries

Terms in the official ICD-10-CM index that lead to Z28.31.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2022 (effective 10/1/2021): Added
  • No changes since FY2022.

Common questions about Z28.31

Is Z28.31 billable?

No. Z28.31 is a header code. Report one of its more specific subcodes instead.