deep vein thrombosis; This spontaneous case was reported by a consumer (subsequently medically confirmed) and describes the occurrence of DEEP VEIN THROMBOSIS (deep vein thrombosis) in a male patient of an unknown age who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 037F21A, 046B21A and 030A21A) for COVID-19 vaccination.     Concurrent medical conditions included Blood pressure high. Concomitant products included LOSARTAN and AMLODIPINE for Blood pressure high.   On 22-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 19-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 07-Sep-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 13-Dec-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced DEEP VEIN THROMBOSIS (deep vein thrombosis) (seriousness criteria hospitalization and medically significant). The patient was hospitalized on 13-Dec-2021 due to DEEP VEIN THROMBOSIS. The patient was treated with HEPARIN (intravenous) for Adverse event, at an unspecified dose and frequency; APIXABAN (ELIQUIS) for Adverse event, at a dose of 20 mg a day for 7days; APIXABAN (ELIQUIS) for Adverse event, at a dose of 10 mg for 3 months and Surgery (Vascular surgery) for Deep vein thrombosis. At the time of the report, DEEP VEIN THROMBOSIS (deep vein thrombosis) was resolving.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 13-Dec-2021, Ultrasound scan: abnormal (abnormal) blood clot-deep vein thrombosis.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   On 13-Dec-2021, the patient was admitted in the hospital for a massive blood clot in left leg. Two weeks earlier started with pain in the left leg which built up constantly until patient could not walk. Leg got swelled quite a bit, it was hard as rock. There were Charlie horse cramps. When patient entered the ER, HCPs made an ultrasound and immediately started preparing patient for vascular surgery. Patient was diagnosed with deep vein thrombosis. HCPs entered the room to exclaim at the ultrasound "oh my god you have a huge horrible blood clot". Patient could not believe having a blood clot because nobody in their family tree had experienced this. The blood clot had extended from mid-thigh all the way to the ankle. Patient received IV heparin. Two more ultrasounds were performed. Patient was getting better. HCPs said that Eliquis is doing its job. Patient did not do anything different to create this, only change was getting Moderna vaccine. Patient stated that no symptoms after first two doses.  Patient is also using a leg compress sock. Company comment:This is a spontaneous case concerning a male patient of an unknown age with medical history of hypertension, who experienced the unexpected serious AESI of Deep vein thrombosis approximately three months after the third dose of mRNA-1273. Rechallenge was not applicable, as this was the third dose. As reported, there were no such complications after the first two doses. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This is a spontaneous case concerning a male patient of an unknown age with medical history of hypertension, who experienced the unexpected serious AESI of Deep vein thrombosis approximately three months after the third dose of mRNA-1273. Rechallenge was not applicable, as this was the third dose. As reported, there were no such complications after the first two doses. The benefit-risk relationship of mRNA-1273 is not affected by this report.