Immunization Encounter ICD-10-CM codes

Z23 (encounter for immunization) is the single diagnosis code for every vaccine: flu, COVID-19, pneumococcal, shingles, Tdap, HPV, childhood series, travel vaccines. Report it once regardless of how many vaccines are given at the visit. The vaccine product (90630 to 90756, or the COVID-19 product codes) and the administration code (90471 to 90474 for commercial patients, G0008, G0009, and G0010 for Medicare flu, pneumococcal, and hepatitis B) carry the detail about which vaccine was given.

Z23 is first-listed when the shot is the only reason for the visit, for example a nurse-only flu shot appointment. When the vaccine is given as part of a well-child check or annual physical, sequence Z00.129 or Z00.00 first and Z23 second; the guidelines allow Z23 as a secondary code whenever the inoculation is a routine part of preventive care. A vaccine given during a problem visit is also reported with Z23 as an additional code.

When a vaccine is due but not given, category Z28 records why: Z28.01 for acute illness, Z28.02 for a chronic condition, Z28.04 for allergy to a vaccine component, Z28.1 for belief-based refusal, Z28.21 for patient refusal, Z28.82 for caregiver refusal, and Z28.83 when the vaccine was unavailable. These codes support the counseling time and the quality measure exclusion. Z28.3x reports underimmunization status, including Z28.310 (unvaccinated for COVID-19) and Z28.311 (partially vaccinated).

Vaccine counseling without administration, such as a parent visit to discuss the schedule, is Z71.85 (encounter for immunization safety counseling). Do not report Z23 when no vaccine was actually administered.