Billing Codes CPT code for vaccine: 90636 CPT Administration code: 90471 Medi-Cal Fee-For-Service (FFS) administration: 90636 ICD-10-CM code (encounter for immunization): Z23 Child Health and Disability Prevention (CHDP) Program Code Conversion (Files.medi-cal.ca.gov/pubsdoco/ CHDP/ARTICES/25768.02_CD_CONV_TABLE.pdf)