This situation is pre-assessed as a medication error/an inappropriate use due to ACT-HIB was reconstituted with sterile water. with no reported adverse event; Initial information received on 15-Jan-2025 regarding an unsolicited valid non-serious case received from a other health professional. This case involves, this situation is pre-assessed as a medication error/an inappropriate use due to a 1 year old female patient received HIB (PRP/T) Vaccine [ACT-HIB] that was reconstituted with sterile water with no reported adverse event. The patient’s past medical history, medical treatment(s), vaccination(s) and family history were not provided. Concomitant medications included Diphtheria Vaccine Toxoid, Pertussis Vaccine Acellular, Tetanus Vaccine Toxoid (DTAP); RSV Vaccine and Pneumococcal Vaccine CONJ for Immunization. On 09-Jan-2025, this situation is pre-assessed as a medication error/an inappropriate use due to the patient received 0.25 ml to 2 ml (once) dose of suspect (standard) HIB (PRP/T) Vaccine Powder and solvent for solution for injection (lot UJ992AA, expiry date: 28-Feb-2025) (unknown strength) via intramuscular route in left thigh for Immunization that was reconstituted with sterile water with no reported adverse event (product preparation error) (latency-same day). Reportedly, Medical assistant reported that she used sterile water instead. She asks if the dose is still valid or do they need to re-administer the dose. 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.