Menactra was accidentally used as the diluent to reconstitute the ProQuad (MMRV) vaccine, and the two were administered together to the patient in one syringe with no adverse event; possible double dose of MENACTRA; When this was discovered, to be sure that the patient actually received Menactra, another Menactra dose was pulled from stock and administered to the patient intramuscularly; Initial information received on 10-Jun-2022 regarding an unsolicited valid non-serious case received via other health professional.  This case involves a 11 years old male patient who experienced menactra was accidentally used as the diluent to reconstitute the proquad (mmrv) vaccine, and the two were administered together to the patient in one syringe with no adverse event and possible double dose of menactra; when this was discovered, to be sure that the patient actually received menactra, another menactra dose was pulled from stock and administered to the patient intramuscularly while receiving vaccines measles vaccine live (enders-edmonston), mumps vaccine live (jeryl lynn), rubella vaccine live (wistar ra 27/3), varicella zoster vaccine live (oka/merck) (Proquad) and meningococcal a-c-y-w135 (d conj) vaccine (Menactra).  The patient's past medical history, medical treatment(s), vaccination(s) and family history were not provided.  Concomitant medications included paracetamol (Tylenol); diphtheria vaccine toxoid, pertussis vaccine acellular, tetanus vaccine toxoid (TDAP); polio vaccine (Polio); influenza vaccine; hpv vaccine and hepatitis a vaccine (Hepatitis A).  On 08-Jun-2022, the patient received a dose of suspect meningococcal a-c-y-w135 (d conj) vaccine at a dose of 0.5 ml with lot U7211AB with expiry date: 13-Apr-2023 via unknown route in unknown administration site for Immunization.  On an unknown date, the patient received a dose of suspect measles vaccine live (enders-edmonston), mumps vaccine live (jeryl lynn), rubella vaccine live (wistar ra 27/3), varicella zoster vaccine live (oka/merck) not produced by Sanofi Pasteur (dose, route, lot number and administration site: unknown) for prophylactic vaccination.  Reportedly on 08-Jun-2022 an HCP in the clinic thought she had pulled only 6 vaccines, but when they checked, she had pulled 7 vaccines from stock for administration to a patient. Menactra was one of the 7 vaccines pulled from stock for administration, but afterward, they were not able to find the Menactra. Therefore, one of two things could have happened. The first is that the Menactra that was pulled from stock was disposed of accidentally, in other words discarded, without being administered to the patient. The second possibility is the Menactra was accidentally used as the diluent to reconstitute the ProQuad (MMRV) vaccine, and the two were administered together to the patient in one syringe (medication error) (event onset: 08-Jun-2022 and latency: unknown). When this was discovered, to be sure that the patient actually received Menactra, another Menactra dose was pulled from stock and administered to the patient intramuscularly (extra dose administered) (event onset: 08-Jun-2022 and latency: unknown), on the same date, but the location on the body where it was administered was not recorded. The ProQuad, which might have also contained a dose of Menactra in it, was administered subcutaneously into the right arm. Treatment provided to the patient was prophylactic around-the-clock Tylenol for 24 hours, which they don't routinely do, but decided to do it this time, just in case the patient might experience injection site soreness or fever. The patient was seen again in the clinic either yesterday (09-Jun-2022) or today (10-Jun-2022), since the patient's brother had an appointment, and the patient had experienced no adverse effects to that point, and was feeling fine.    Action taken: not applicable.   Outcome: unknown   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 guidelines. 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.