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Z28.310 ICD-10-CM Code: Unvaccinated for COVID-19

Compare with another code for Z28.310Check this code on a claim

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
1 inclusion term · 5 use-additional codes · 1 code-also instruction

Billable · FY2027A valid, specific ICD-10-CM code, reportable for dates of service in FY2027.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too, and is marked with where it comes from.

Use additional codefrom Z28.3Report with this code when documented
  • Use additional 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)

+1 more in Instructions

Code alsofrom Z28May be needed with this code
  • Code also, if applicable, encounter for immunization safety counseling (Z71.85)
Includesfrom Z28What Z28 covers
  • vaccination not carried out

Where it sits Source: CMS/NCHS

Under:Chapter 21: Factors Influencing Health Status and Contact with Health ServicesZ20-Z29 Persons with potential health hazards related to communicable diseasesZ28 Immunization not carried out and underimmunization statusZ28.3 Underimmunization statusZ28.31 Underimmunization for COVID-19 status

Most relevant related codes MedCoder-derived

Read off the official notes above and this code’s own position in the tabular list. Which to report is a documentation question; Compare shows the two side by side.

CompareCheck ClaimView Related Codes

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

  • MS-DRG 951 — OTHER FACTORS INFLUENCING HEALTH STATUS (MDC 23)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Z28.310 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on Z28.310 itself; “inherited from” names the category or block whose note applies here.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • vaccination not carried out

Source: inherited from Z28

Code Also

Additional codes that may be required to fully describe the encounter.

  • Code also, if applicable, encounter for immunization safety counseling (Z71.85)

Source: inherited from Z28

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional 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-)

Source: inherited from Z28.3

Coder workflow for Z28.310

MedCoder structured workflow — derived from this code’s own official record

Before you code Z28.310

  1. Confirm the reason for the encounter this Z code records: a status — a condition, carrier state or sequela that may affect care, distinct from a current complication of it. Check whether the code may be reported as first-listed or principal — some Z codes are limited to one position — and do not report a history or status code for a condition documented as current. Z code categories and their reporting positions (Guidelines I.C.21.c.3, I.C.21.c.15).

    Guide: Status codes (Z codes) →

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.
The reason for the encounter
Whether the code records the encounter’s purpose, a status, or a history — and whether it may be first-listed (Guidelines I.C.21.c).

Official instructions as workflow

  • Use Additional Code — after identifying Z28.310(5 notes)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with Z28.310 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewZ28.0, Z28.2, Z28.1, Z28.8

    See the official tabular notes · Guidelines I.A.13

  • Code Also — related condition(1 note)

    Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

    ReviewZ71.85

    See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with Z28.310?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

ReviewZ28.0, Z28.2, Z28.1, Z28.8

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Unvaccinated for COVID-19 is a billable ICD-10-CM diagnosis code (Z28.310).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Chapter 1: Certain Infectious and Parasitic Diseases (A00-B99), U07.1, U09.9 a. Human Immunodeficiency Virus (HIV) Infections 1) Code only confirmed cases

(n) Underimmunization for COVID-19 Status Code Z28.310, Unvaccinated for COVID-19, may be assigned when the patient has not received a COVID-19 vaccine of any type. Code Z28.311, Partially vaccinated for COVID-19, may be assigned when the patient has been partially vaccinated for COVID-19 as per the recommendations of the Centers for Disease Control and Prevention (CDC) in place at the time of the encounter. For information, visit the CDC’s website https://www.cdc.gov/covidschedule.

Chapter 21: Factors influencing health status and contact with health services (Z00-Z99)

Codes from category Z15 should generally not be used as principal or first-listed codes. If the patient has the condition to which he/she is susceptible, and that condition is the reason for the encounter, the code for the current condition should be sequenced first. If the patient is being seen for follow-up after completed treatment for this condition, and the condition no longer exists, a follow-up code should be sequenced first, followed by the appropriate personal history and genetic susceptibility codes. If the purpose of the encounter is genetic counseling associated with procreative management, code Z31.5, Encounter for genetic counseling, should be assigned as the first-listed code, followed by a code from category Z15. Additional codes should be assigned for any applicable family or personal history. Z16 Resistance to antimicrobial drugs This category indicates that a patient has a condition that is resistant to antimicrobial drug treatment. Sequence the infection code first. Z17 Estrogen, and other hormones and factors receptor status Z18 Retained foreign body fragments Z19 Hormone sensitivity malignancy status Z21 Asymptomatic HIV infection status This code indicates that a patient has tested positive for HIV but has manifested no signs or symptoms of the disease. Z22 Carrier of infectious disease Carrier status indicates that a person harbors the specific organisms of a disease without manifest symptoms and is capable of transmitting the infection. Z28.3 Underimmunization status

Chapter 21: Factors influencing health status and contact with health services (Z00-Z99)

Miscellaneous Z codes/subcategories/categories: Z28 Immunization not carried out Except: Z28.3-, Underimmunization status Z29 Encounter for other prophylactic measures Z40 Encounter for prophylactic surgery Z41 Encounter for procedures for purposes other than remedying health state Except: Z41.9, Encounter for procedure for purposes other than remedying health state, unspecified Z53 Persons encountering health services for specific procedures and treatment, not carried out Z72 Problems related to lifestyle Note: These codes should be assigned only when the documentation specifies that the patient has an associated problem Z73 Problems related to life management difficulty Note: These codes should be assigned only when the documentation specifies that the patient has an associated problem. Z74 Problems related to care provider dependency Except: Z74.01, Bed confinement status Z75 Problems related to medical facilities and other health care Z76.0 Encounter for issue of repeat prescription

Verify Before Coding

  • Principal-diagnosis restriction. The Medicare Code Editor lists this code as unacceptable as a principal diagnosis: it describes a circumstance influencing health status rather than a current illness or injury being treated. It is valid as a secondary diagnosis.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name Z28.310 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Code Also instruction: Z71.85 — Encounter for immunization safety counseling (via Z28.-).

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 1 MS-DRG: DRG 951 (MDC 23).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):FAC017 — No immunization or underimmunization.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Principal diagnosis restriction (Medicare Code Editor)

Not acceptable as a principal diagnosis on an inpatient claim.

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (No immunization or underimmunization).

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, Z28.20 — 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 status, Z28.311 — Partially vaccinated for COVID-19, Z28.39 — Other underimmunization status, 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

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Status”, “COVID-19”; these codes share that main term but sit in a different category of the Tabular List.

Z17.31 — Human epidermal growth factor receptor 2 positive status (human epidermal growth factor 2 receptor, positive), Z17.32 — Human epidermal growth factor receptor 2 negative status (human epidermal growth factor 2 receptor, negative), Z17.410 — Hormone receptor positive with human epidermal growth factor receptor 2 positive status (combined receptor, positive, hormone receptor positive with human epidermal growth factor receptor 2 positive), Z17.411 — Hormone receptor positive with human epidermal growth factor receptor 2 negative status (combined receptor, positive, hormone receptor positive with human epidermal growth factor receptor 2 negative), Z17.420 — Hormone receptor negative with human epidermal growth factor receptor 2 positive status (combined receptor, negative, hormone receptor negative with human epidermal growth factor receptor 2 positive), Z17.421 — Hormone receptor negative with human epidermal growth factor receptor 2 negative status (combined receptor, negative, hormone receptor negative with human epidermal growth factor receptor 2 negative), Z19.1 — Hormone sensitive malignancy status (malignancy, hormone sensitive), Z19.2 — Hormone resistant malignancy status (malignancy, hormone resistant), Z20.822 — Contact with and (suspected) exposure to COVID-19 (contact), Z21 — Asymptomatic human immunodeficiency virus [HIV] infection status (human immunodeficiency virusinfection, asymptomatic), Z33.1 — Pregnant state, incidental (pregnancy, incidental), Z39.0 — Encounter for care and examination of mother immediately after delivery (postpartum, care immediately after delivery), Z39.2 — Encounter for routine postpartum follow-up (postpartum), Z56.82 — Military deployment status (deployment), Z66 — Do not resuscitate (do not resuscitate), Z74.01 — Bed confinement status (bed confinement), Z76.82 — Awaiting organ transplant status (awaiting organ transplant), Z78.1 — Physical restraint status (physical restraint), Z86.16 — Personal history of COVID-19 (history of), Z87.890 — Personal history of sex reassignment (sex reassignment surgery status), +83 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Blood Glucose Test, Thyroid Stimulating Hormone (TSH)

Contextual Map

Every relationship of Z28.310 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run Z28.310 with this related code in Claim Check

Hierarchy

Referenced by Code Also instructions

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 23 — Factors Influencing Health Status and Other Contacts with Health Services[MDC crossing]: “Factors Influencing Health Status and Other Contacts with Health Services — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 1,258 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Index entries

  • COVID-19, unvaccinated (for)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Status (post), underimmunization, COVID-19, unvaccinated (for)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Underimmunization status, COVID-19, unvaccinated (for)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Unimmunized, for COVID-19[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Unvaccinated, for COVID-19[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027

Nearest codes (22)

Change history

Relevant guides

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Indexed Clinical Terms (5)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Coding guidelines Official source data
ICD-10-CM Official Guidelines for Coding and Reporting (FY2027), quoted by section Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder-derived relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder editorial explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "Z28.310 — Unvaccinated for COVID-19." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/z28.310-unvaccinated-for-covid-19

Change history

  • FY2022 — October 1, 2021
    Added to the code set
    Unvaccinated for COVID-19
    FY2022 changes

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Z28.310 in its code family, with their registry titles.

View all codes in the Z28 family