ICD10

ICD-10 Code Z28.31: Underimmunization for COVID-19 status

Z28.31 is an ICD-10 diagnosis entry used to group records related to Underimmunization for COVID-19 status. You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen. ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Factors influencing health status and contact with health services (Z00-Z99).

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Factors influencing health status and contact with health services (Z00-Z99).

When is it used?

  • May be used when a clinician documents underimmunization for covid-19 status in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
  • This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

chapter
21Factors influencing health status and contact with health services (Z00-Z99)
block
Z20-Z29Persons with potential health hazards related to communicable diseases
category
Z28Immunization not carried out and underimmunization status
category
Z28.3Underimmunization status
currentZ28.3

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

General Physician

Coding guidelines

Common synonyms

Underimmunization for COVID-19 status

Frequently asked questions

Code details

CodeZ28.31
SystemICD10
Display nameUnderimmunization for COVID-19 status
ChapterFactors influencing health status and contact with health services (Z00-Z99)
BlockPersons with potential health hazards related to communicable diseases

Flags

BillableNo
Valid clinical useNo

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.

ICD-10 Code Z28.31 for Underimmunization for COVID-19 status | HealthAssure