2027 ICD-10-CM Diagnosis Code Z28.311Partially vaccinated for COVID-19

ICD-10-CM Codes›Z00–Z99›Z20-Z29›Z28

ICD-10-CM Z28.311
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Z28.311 is a billable ICD-10-CM diagnosis code for partially vaccinated for COVID-19. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 951. The code is not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. Coders also document this condition as immunization series incomplete. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under No immunization or underimmunization.

Code Identity

ICD-10-CM Code
Z28.311
Billable Status
Yes — Valid for Submission
Code Describes
Partially vaccinated for COVID-19
Short Description
Partially vaccinated for COVID-19
Same as the full description in the CMS dataset.
Parent Code
Z28.31
Underimmunization for COVID-19 status

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 CodeZ28.311Partially vaccinated for COVID-19

Code EditsBilling

Medicare Code Editor checks that affect claim validity for Z28.311.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Present on Admission (POA)Billing

Z28.311 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Persons with potential health hazards related to communicable diseases (Z20-Z29).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Immunization series incomplete
  • Partial vaccination for COVID-19
  • Requires first booster dose of SARS-CoV-2 vaccine
  • Requires second booster dose of SARS-CoV-2 vaccine
  • Requires third booster dose of SARS-CoV-2 vaccine
  • SARS-CoV-2 initial immunization series incomplete

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Z28.311: its own notes plus those printed at Z28.31, Z28.3, Z28, and 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.

From Z28 Immunization not carried out and underimmunization status applies to 17 codes
  • vaccination not carried out

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Z28.3 Underimmunization status applies to 3 codes
  • 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-)

Code Also

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

From Z28 Immunization not carried out and underimmunization status applies to 17 codes
  • if applicable, encounter for immunization safety counseling (Z71.85)

Notes

General instructions on how these codes are used.

From Z28.31 Underimmunization for COVID-19 status applies to 2 codes
  • These codes should not be used for individuals who are not eligible for the COVID-19 vaccines, as determined by the healthcare provider.
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 Z28.311, its category, or a range that includes it.

Code Also 1

These codes say Z28.311 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.-) names Z28.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR FAC017
No immunization or underimmunization
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Partially Vaccinated for COVID-19

    a status indicating that an individual has received a covid-19 vaccination but has not completed a vaccination series.

Patient EducationClinical

COVID-19 Vaccines

COVID-19 (coronavirus disease 2019) is an illness caused by a virus. This virus is a coronavirus called SARS-CoV-2. Most people with COVID-19 have mild symptoms, but some people become very sick. You can protect yourself by getting a COVID-19 vaccine. The vaccines might help keep you from getting sick from COVID-19.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement Z28.311 replaces the following previously assigned code(s):

  • Z28.3 - Underimmunization status
FY 2023AddedAdded to the ICD-10-CM code setEffective October 1, 2022.
FY 2024–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Z28.311Overview

What is the ICD-10 code for partially vaccinated for COVID-19?

The ICD-10-CM code for partially vaccinated for COVID-19 is Z28.311 (sometimes written as Z28311). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is Z28.311 (Underimmunization for COVID-19 status) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report partially vaccinated for COVID-19 on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does Z28.311 group to?

On inpatient claims, partially vaccinated for COVID-19 maps to MS-DRG 951 (other Factors Influencing Health Status), which carries a relative weight of 0.5574. Higher weights mean higher Medicare reimbursement.

Can Z28.311 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because partially vaccinated for COVID-19 describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

Is Z28.311 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for partially vaccinated for COVID-19 on inpatient claims. The code appears in the Persons with potential health hazards related to communicable diseases (Z20-Z29) range of the CMS exempt list.