Cyanocobalamin Injection USP 1000 mcg mL Injection and Infusion Coding: What You NEED to Know! Not all injections are created equal and in the CPT Medicine section, the difference between an IV infusion, an IM injection, What is the correct code for the administration of one vaccine given intramuscularly for a child under eight years of age when the physician counsels the parents? In the CPT Index, look CPT Code 90471: Immunization Administration Billing Guide 96372 CPT Code: Injection of drug substance under skin or into muscle