venous thromboembolism; This literature-non-study case was reported in a literature article and describes the occurrence of EMBOLISM VENOUS (venous thromboembolism) in a 79-year-old male patient who received mRNA-1273 (Spikevax) for COVID-19 vaccination.   No Medical History information was reported.   On an unknown date, the patient received second dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date, received first dose of mRNA-1273 (Spikevax) (unknown route) dosage was changed to 1 dosage form. On an unknown date, the patient experienced EMBOLISM VENOUS (venous thromboembolism) (seriousness criteria hospitalization and medically significant). At the time of the report, EMBOLISM VENOUS (venous thromboembolism) outcome was unknown.        For mRNA-1273 (Spikevax) (Unknown), the reporter considered EMBOLISM VENOUS (venous thromboembolism) to be related.    A patient suddenly developed right lower extremity (RLE) pain and swelling a few days after receiving his 1st dose of the mRNA-1273 COVID-19 vaccine.   Investigations confirmed extensive acute deep venous thrombosis and a concurrent acute pulmonary embolism.  Therapeutic anticoagulation was initiated and patient was eventually discharged home on supplemental oxygen  No concomitants and treatment were reported. . Company Comment: This literature non-study case concerns a 79-year-old male patient, with no reported medical history, who experienced the unexpected serious (hospitalization and medically significant) AESI of Embolism venous. Patient suddenly developed right lower extremity pain and swelling below the knee 3 days after receiving the 1st dose of the mRNA-1273 vaccine. 28 days after the 1st dose, patient received the 2nd dose of mRNA-1273 vaccine. Symptoms worsened with accompanying shortness of breath which led him to complete doppler venous ultrasound of right lower extremity demonstrating an acute deep vein thrombosis in the right trunks, right popliteal vein, right femoral vein, and right peroneal vein. Patient subsequently sought emergency consult. Vital signs: BP of 187/83 with HR of 85, afebrile, hypoxic to 87% on room air requiring supplemental oxygen. COVID_19 RT-PCR test negative. Shortly after, patient developed atrial fibrillation with HR of 142 controlled with beta-blockers. Computed tomography angiography of the chest revealed an acute subsegmental right lower lobe pulmonary embolism. Echocardiogram and Troponin normal. Blood tests within standard limits except for D-dimer elevated to 1.22 ug/ml. Therapeutic anticoagulation with heparin initiated and admitted to a closely monitored unit. Patient was eventually discharged home on supplemental oxygen and Apixaban. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This literature non-study case concerns a 79-year-old male patient, with no reported medical history, who experienced the unexpected serious (hospitalization and medically significant) AESI of Embolism venous. Patient suddenly developed right lower extremity pain and swelling below the knee 3 days after receiving the 1st dose of the mRNA-1273 vaccine. 28 days after the 1st dose, patient received the 2nd dose of mRNA-1273 vaccine. Symptoms worsened with accompanying shortness of breath which led him to complete doppler venous ultrasound of right lower extremity demonstrating an acute deep vein thrombosis in the right trunks, right popliteal vein, right femoral vein, and right peroneal vein. Patient subsequently sought emergency consult. Vital signs: BP of 187/83 with HR of 85, afebrile, hypoxic to 87% on room air requiring supplemental oxygen. COVID_19 RT-PCR test negative. Shortly after, patient developed atrial fibrillation with HR of 142 controlled with beta-blockers. Computed tomography angiography of the chest revealed an acute subsegmental right lower lobe pulmonary embolism. Echocardiogram and Troponin normal. Blood tests within standard limits except for D-dimer elevated to 1.22 ug/ml. Therapeutic anticoagulation with heparin initiated and admitted to a closely monitored unit. Patient was eventually discharged home on supplemental oxygen and Apixaban. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.