2026 ICD-10-CM Diagnosis Code T88.1XXSOther complications following immunization, not elsewhere classified, sequela
T88.1XXS is a billable ICD-10-CM diagnosis code for other complications following immunization, not elsewhere classified, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complication, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T88.1XXS is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Complication due to immunization
- Complication due to vaccination
- Complication of smallpox vaccination
- Eczema vaccinatum
- Feeling irritable
- Fibrosarcoma
- Generalized vaccinia
- Inadvertent autoinoculation with Vaccinia virus following contact with smallpox vaccination site
- Infection following immunization
- Inflammatory neuropathy due to and following vaccination
- Irritability postvaccinal
- Kaposi's varicelliform eruption caused by Vaccinia virus
- Neurological complication following vaccination
- Progressive vaccina
- Scar of skin following first vaccination
- Swelling of skin
- Vaccination site cellulitis
- Vaccination site lump
- Vaccination site rash
- Vaccination site swelling
- Vaccination site vaccinia
- Vaccine-induced fibrosarcoma
- Vaccinia
- Vaccinia keratitis
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Other complications of surgical and medical care, not elsewhere classified (T88). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Dual Specificity Phosphatase 3
a dual specificity phosphatase subtype that plays a role in intracellular signal transduction by inactivating mitogen-activated protein kinases. it has specificity for extracellular signal-regulated map kinases.Smallpox Vaccine
a vaccinia virus vaccine used for immunization against smallpox. it is now recommended only for laboratory workers exposed to smallpox virus. certain countries continue to vaccinate those in the military service. rare complications most often associated with older generation smallpox vaccines include vaccinia, secondary bacterial infections, and encephalomyelitis. because monkeypox virus and smallpox virus are both orthopoxvirus and are closely related smallpox vaccines provide effective cross-protection against mpox, monkeypox (https://www.cdc.gov/poxvirus/monkeypox/clinicians/smallpox-vaccine.html).Vaccinia
the cutaneous and occasional systemic reactions associated with vaccination using smallpox (variola) vaccine.Vaccinia virus
the type species of orthopoxvirus, related to cowpox virus, but whose true origin is unknown. it has been used as a live vaccine against smallpox. it is also used as a vector for inserting foreign dna into animals. rabbitpox virus is a subspecies of vaccinia virus.Dermatofibrosarcoma
a sarcoma of the deep layers of the skin. the tumors are locally aggressive tends to recur but rarely metastatic. it can be classified into variants depending on the cell type tumors are derived from or by its characteristics: pigmented variant from melanin-containing dermal dendritic cells; myxoid variant, myxoid stromal cells; giant cell variant characterized by giant cells in the tumors; and fibrosarcomatous variant chracterized by tumor areas histologically indistinguishable from fibrosarcoma.Fibrosarcoma
a sarcoma derived from deep fibrous tissue, characterized by bundles of immature proliferating fibroblasts with variable collagen formation, which tends to invade locally and metastasize by the bloodstream. (stedman, 25th ed)
Patient EducationClinical
Vaccines
Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. For example, there are vaccines to protect against diseases caused by:
The full article covers:
- What are vaccines?
- What are the types of vaccines?
- What happens in an immune response?
- What are immunization and vaccination?
- Why are vaccines important?
- What is community immunity?
- Are vaccines safe?
- What is a vaccine schedule?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T88.1XXS to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T88.1XXSOverview
Is T88.1XXS a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other complications following immunization, not elsewhere classified, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T88.1XXS mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the other complications following immunization, not elsewhere classified itself has resolved, not the original event.
What MS-DRG does T88.1XXS group to?
When other complications following immunization, not elsewhere classified, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T88.1XXS 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 other complications following immunization, not elsewhere classified, sequela on inpatient claims.
What is the ICD-9 equivalent of T88.1XXS?
Under the General Equivalence Mappings, other complications following immunization, not elsewhere classified, sequela converts to ICD-9-CM 909.3 (late eff surg/med compl). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
