inappropriate use due to only the diluent of ACT-HIB was given to a patient with no reported adverse event; Initial information received on 28-Jan-2025 regarding an unsolicited valid non-serious case received from a Other health professional. This case involves, the inappropriate use due to only the diluent of HIB (PRP/T) Vaccine [ACT-HIB] was given to a patient with no reported adverse event. The patient’s past medical history, medical treatment(s), vaccination(s) and family history were not provided. On an unknown date, the inappropriate use due to only the diluent of HIB (PRP/T) Vaccine Powder and solvent for solution for injection (unknown strength, dosage, expiry date, batch number and route) via unknown administration site for prophylactic vaccination was given to a patient with no reported adverse event (single component of a two-component product administered) (unknown latency). Information on the batch number was requested corresponding to the one at time of event occurrence. Reportedly, Supervisor did not have the patient’s information at the time of the call. This suspected adverse reaction report is submitted and classified as a medication error solely and exclusively to ensure the marketing authorization holder’s compliance with the requirements set out in the Directive 2001/83/EC and Module VI of the Good Pharmacovigilance Practices. The classification as a medical error is in no way intended, nor should it be interpreted or construed as an allegation or claim made by the marketing authorization holder that any third party has contributed to or is to be held liable for the occurrence of this medication error.