caller unsure if patient received full amount of dose as some of the diluent leaked out due to the suction; syringe experienced suction when twisting the needle onto the hub of syringe causing cap; caller unsure if patient received full amount of dose as some of the diluent leaked out due to the suction; device fluid leak; no adverse event; This spontaneous report was received from registered nurse and refers to a 15-month-old. patient of unknown gender. The patient’s medical history was not reported. The patient’s concurrent conditions were not reported. Concomitant therapies were not reported. On an unknown date, the patient started therapy with measles, mumps, and rubella (wistar ra 27-3) virus vaccine, live (M-M-R II) injection, lot #Y010046, expiration date: 29-MAY-2026, administered for prophylaxis (strength, and route of administration were not provided), status albumin- rHA; and sterile diluent (BAXTER STERILE DILUENT) solution for injection/infusion, lot #1973242, expiration date: 17-FEB-2026 (strength, route of administration, and indication were not provided). On an unknown date, the sterile diluent syringe experienced suction when twisting the needle onto the hub of syringe causing cap of syringe to pop off. The nurse reported that a dose of M-M-R-II was administered to a patient that was reconstituted using the defective sterile diluent syringe and caller unsure if patient received full amount of dose as some of the diluent leaked out due to the suction. No adverse events reported.