half of the dose given due to plunger broke with no reported adverse event; plunger broke with no reported adverse event; Initial information regarding an unsolicited valid non-serious case was received from the other health care professional via Regulatory authority (Reference number- 00690029) and transmitted to Sanofi on 19-Jul-2021.  This case involves a 10 year old female patient to whom half of the dose was given due to plunger broke with no reported adverse event (Underdose) and plunger broke with no reported adverse event (Syringe issue) at the time of receiving vaccine DIPHTHERIA-2/TETANUS/5 AC PERTUSSIS VACCINE [ADACEL].  The patient's medical history, past medical treatment(s), vaccination(s) and family history were not provided.  On 19-Jul-2021, the patient received a dose (0.3ml) of suspect DIPHTHERIA-2/TETANUS/5 AC PERTUSSIS VACCINE (lot number: U6968AA; expiry date: 07-Feb-2023) via intramuscular route in the left arm for prophylactic vaccination.  It was case of vaccine under dose and syringe issue (latency: same day).  It was reported, "we just have a question a Tdap (DIPHTHERIA-2/TETANUS/5 AC PERTUSSIS) Adacel vaccine was given to a child, and the vaccine was broken so the MA (medical assistant) vaccinated the patient but the plunger broke um inside when the needle was inside and then plunger broke so that only half of the dose was given to the patient. So we have 2 questions, one we need to get this defective vaccine replaced and then two we needed to have um a nurse to call us back and let us know if the patient needs to be given another dose of the Tdap Adacel"  Also, it was reported, "a medical assistant was administering an Adacel vaccine to a patient on 19jul2021. When she was administering the Adacel syringe broke right away (possible the plunger rod)  and she was only able to give 0.3ml of the medicine. Caller states that she will send pictures because she is not sure what part it is. Number of units affected:1. Is dose not used or not available: yes. Whether product is available for return: no. No broken vials or syringes with needles can be returned. Plungers: First question if plunger fell out - Were you trying to aspirate: No. If loose-did vaccine leak out the barrel: No. Was the plunger intact upon opening the carton: Yes. Difficulty pushing the plunger during administration: yes Broken vial or syringe (these questions should also apply to cracked vials or syringes). State where it is broken or cracked according to the diagram: Plunger rod. Broke or cracked during preparation or use: Use. Received broken or cracked in the carton: No. Was there any damage to the carton upon receipt: No. Was there any product residue in the carton: No. Were there any signs of damage to any other vial in the carton: No"  At the time of reporting, the  no adverse event were reported.  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.