patient who was due to get a shot of PENTACEL but the provider only administered the diluent part of the product with no reported adverse event; Patient was administered with 2 doses of the diluents back to back with about a 5 minute interval; Initial information received on 23-Jan-2025 regarding an unsolicited valid non-serious case received from a physician. This case involves a 6 months old male patient who was administered with the diluent part of the diphtheria/tetanus/5 HYBRID AC pertussis/IPV(VERO)/HIB(PRP/T) vaccine [Pentacel (VERO)] and patient was administered with 2 doses of the diluents back to back with about a 5 minute interval with no reported adverse event. The patient’s past medical history, medical treatment(s), vaccination(s) and family history were not provided. On 23-Jan-2025, the patient received the diluent part of the diphtheria/tetanus/5 HYBRID AC pertussis/IPV(VERO)/HIB(PRP/T) vaccine Suspension for injection with standard strength (expiry date, lot number and dose not reported) via unknown route in unknown administration site as Immunization (single component of a two-component product administered) and was administered with 2 doses of the diluents back to back with about a 5 minute interval (extra dose administered) (same day latency). Reportedly, caller asked on the dosing for the patient’s next dose, since the patient was supposed to get it at 18 months, they wanted to know if the patient should only be given with Hib since the patient already got 2 doses of the DTAP-IPV. Information on the batch number was requested corresponding to the one at time of event occurrence. 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.