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ICD-10-CM T88.1XXA: Other complications following immunization, not elsewhere classified, initial encounter

T88.1XXA is the billable ICD-10-CM code for other complications following immunization, not elsewhere classified, initial encounter, in category T88 (Other complications of surgical and medical care, not elsewhere classified) of the Complications of surgical and medical care, not elsewhere classified section. As a principal diagnosis it groups to MS-DRG 865 Viral Illness with MCC, MS-DRG 866 Viral Illness without MCC (MDC 18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites). As a secondary diagnosis it is a CC, excluded with 1 principal diagnoses. 1 LCD billing and coding article lists it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
T88.1XXA
billable FY2027 ICD-10-CM code
Category
T88 Other complications of surgical and medical care, not elsewhere classified
Chapter
19: Injury, poisoning and certain other consequences of external causes (S00-T88)
CC/MCC (MS-DRG v44)
CC
CMS-HCC V28
Not mapped
POA reporting
Required

Tabular list notes for T88.1XXA

The tabular list has no notes on T88.1XXA itself; the notes below apply from its parent headings.

Inherited from T88 (Other complications of surgical and medical care, not elsewhere classified)

Excludes2 (not part of this condition, may be coded together)
  • complication following infusion, transfusion and therapeutic injection (T80.-)
  • complication following procedure NEC (T81.-)
  • complications of anesthesia in labor and delivery (O74.-)
  • complications of anesthesia in pregnancy (O29.-)
  • complications of anesthesia in puerperium (O89.-)
  • complications of devices, implants and grafts (T82-T85)
  • complications of obstetric surgery and procedure (O75.4)
  • dermatitis due to drugs and medicaments (L23.3, L24.4, L25.1, L27.0-L27.1)
  • poisoning and toxic effects of drugs and chemicals (T36-T65 with fifth or sixth character 1-4)
  • specified complications classified elsewhere

Inherited from T88.1 (Other complications following immunization, not elsewhere classified)

Inclusion terms
  • Generalized vaccinia
  • Rash following immunization
Excludes1 (never coded together)
  • vaccinia not from vaccine (B08.011)
Excludes2 (not part of this condition, may be coded together)
  • anaphylactic shock due to serum (T80.5-)
  • other serum reactions (T80.6-)
  • postimmunization arthropathy (M02.2)
  • postimmunization encephalitis (G04.02)
  • postimmunization fever (R50.83)

The 7th character A means “initial encounter”, as defined at T88. The same injury coded for a later encounter uses a different 7th character, so check each encounter.

MS-DRG grouping when T88.1XXA is the principal diagnosis

MS-DRG v44 groups for T88.1XXA as principal diagnosis
MDCMS-DRGs
18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites865866

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for T88.1XXA shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, T88.1XXA is a CC under MS-DRG v44, unless the principal diagnosis is one of the 1 codes in its exclusion list. Check T88.1XXA against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.

CMS-HCC V28 risk adjustment

T88.1XXA does not map to a payment HCC in the PY2027 CMS-HCC V28 model, so on its own it does not change a Medicare Advantage risk score.

LCD billing and coding articles that list T88.1XXA

1 current Medicare billing and coding article lists T88.1XXA among the diagnoses that support medical necessity for the services they cover.

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Frequently asked questions

What does ICD-10-CM T88.1XXA mean?

T88.1XXA means other complications following immunization, not elsewhere classified, initial encounter. It is one of 25 billable codes under T88, other complications of surgical and medical care, not elsewhere classified.

What can't be coded with T88.1XXA?

Excludes1 at T88.1: vaccinia not from vaccine (B08.011). These are never reported together with T88.1XXA.

Which MS-DRG does T88.1XXA group to?

As the principal diagnosis, T88.1XXA groups to MS-DRG 865 Viral Illness with MCC, MS-DRG 866 Viral Illness without MCC (MDC 18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Is T88.1XXA a CC or MCC?

T88.1XXA is a CC under MS-DRG v44; 1 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.