ICD-10-CM 2027
ICD-10 code for Flu shot
Confirmed by the official ICD-10-CM index entry “immunization › encounter for”. Page updated September 29, 2026.
About coding Flu shot
The ICD-10-CM code for Flu shot is Z23 (Encounter for immunization).
It is also searched as vaccine, vaccination.
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.
Common questions about Flu shot ICD-10 codes
What is the ICD-10 code for Flu shot?
- Z23 — Encounter for immunization.
Is Z23 billable?
- Yes. Z23 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Z23 be used as a principal diagnosis?
- No. It is not acceptable as the principal diagnosis for an inpatient stay; it may be reported as a secondary diagnosis.
Is Z23 a CC or MCC?
- No. Z23 is neither a CC nor an MCC under MS-DRG v44.0.