Summary & Overview
HCPCS M1173: Td/Tdap Immunization Gap Identified
HCPCS Level II code M1173 identifies patients who did not receive at least one Td or Tdap vaccine during the period from nine years before the encounter through the end of the measurement period. This code captures missed opportunities for updating tetanus-containing immunizations and is used in preventive care quality measurement and reporting. Nationally, tracking Td/Tdap vaccination gaps is important for outbreak prevention and maintaining adult immunization coverage.
The analysis covers major national payers including Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an explanation of what the code represents, the clinical context for Td and Tdap immunization gaps, and what measures and benchmarks typically relate to this code. The publication summarizes typical service settings and operational implications for documentation and reporting. It also outlines common areas where payers and quality programs focus, such as measurement windows, eligibility criteria, and the role of electronic health record reconciliation in identifying eligible patients.
Data not available in the input for payer-specific rates, associated taxonomies, ICD-10 diagnoses, related codes, and service line details.
Billing Code Overview
HCPCS Level II code M1173 indicates that a patient did not receive at least one tetanus-diphtheria (Td) vaccine or one tetanus-diphtheria-acellular pertussis (Tdap) vaccine between nine years prior to the encounter and the end of the measurement period. This reflects a gap in recommended adult immunization for tetanus-containing vaccines within the specified retrospective window.
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Service type: Immunization gap assessment / preventive care documentation
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Typical site of service: Outpatient clinics, primary care offices, and preventive care visits where vaccination history and immunization status are reviewed
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Clinical & Coding Specifications
Clinical Context
A 42-year-old adult presents to a primary care clinic for an annual wellness visit. The patient’s immunization record indicates no documented tetanus-diphtheria (Td) or tetanus-diphtheria-acellular pertussis (Tdap) vaccination in the past nine years. During the visit, the nurse reviews immunization history, screens for contraindications (e.g., severe allergic reaction to a prior tetanus-containing vaccine, encephalopathy), documents informed refusal if applicable, and offers vaccination. If the patient declines or vaccination cannot be administered (e.g., acute febrile illness), the encounter is coded to indicate the patient did not receive at least one Td or Tdap vaccine during the nine-year measurement window. Typical clinical workflow includes chart review, assessment of vaccine history, counseling, administration of vaccine if accepted, documentation of lot number/site/expiration, and billing for vaccine administration or for the encounter reason if vaccine not given. Typical sites of service are ambulatory primary care clinics, community health centers, urgent care centers, and school-based health clinics. Common clinical personnel involved include primary care physicians, nurse practitioners, physician assistants, registered nurses, and medical assistants.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
22 | Increased procedural services | Use when additional work beyond the usual service is documented (e.g., extended counseling about immunization risks and benefits). |