Z23Encounter for immunization

Z23 is the ICD-10-CM diagnosis code for encounter for immunization. It belongs to block Z20-Z29 (persons with potential health hazards related to communicable diseases) and chapter 21 (factors influencing health status and contact with health services). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Code first: any routine childhood examination.

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 795 (Normal Newborn, relative weight 0.2022) and DRG 951 (Other Factors Influencing Health Status, relative weight 0.5577), in MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period) and MDC 23 (Factors Influencing Health Status and Other Contacts with Health Services), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It is not acceptable as the principal diagnosis for an inpatient stay; it may be reported as a secondary diagnosis.

It is exempt from present-on-admission (POA) reporting, so no POA indicator is required.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as V05.9 (Need for prophylactic vaccination and inoculation against unspecified single disease).