Portal vein thrombosis; This literature-non-study case was reported in a literature article and describes the occurrence of PORTAL VEIN THROMBOSIS (Portal vein thrombosis) in a 51-year-old male patient who received mRNA-1273 (Spikevax) for COVID-19 prophylaxis.   The patient's past medical history included Non-smoker and Coronary angioplasty. Concurrent medical conditions included Diabetes, Obesity, Hyperlipidemia, Hypertension and Coronary artery disease. Concomitant products included INSULIN, METFORMIN, AMLODIPINE, BENAZEPRIL, ROSUVASTATIN and CITALOPRAM for an unknown indication.    On an unknown date, the patient received first dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date,  after starting mRNA-1273 (Spikevax), the patient experienced PORTAL VEIN THROMBOSIS (Portal vein thrombosis) (seriousness criteria hospitalization and medically significant). The patient was treated with HEPARIN at an unspecified dose and frequency; APIXABAN at a dose of 10 milligram twice a day and APIXABAN ongoing since an unknown date at a dose of 5 milligram twice a day. At the time of the report, PORTAL VEIN THROMBOSIS (Portal vein thrombosis) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 25-Apr-2019, Platelet count: 134 10 thousand per microlitre. On 01-Feb-2021, Platelet count: 133 10 thousand per microlitre. On 10-Mar-2021, Platelet count: 130 10 thousand per microlitre. On 28-Jun-2021, Platelet count: 144 10 thousand per microlitre. On 29-Jun-2021, Platelet count: 121 10 thousand per microlitre. On 30-Jun-2021, Platelet count: 124 10 thousand per microlitre. On 05-Jul-2021, Platelet count: 153 10 thousand per microlitre. On 14-Jul-2021, Platelet count: 135 10 thousand per microlitre. On 28-Nov-2021, Platelet count: 121 10 thousand per microlitre. On an unknown date, Activated protein C resistance test: (Negative) negative for Factor V Leiden. On an unknown date, Alanine aminotransferase: 31 international unit per litre. On an unknown date, Alpha 1 foetoprotein: Normal. On an unknown date, Alpha-1 anti-trypsin: Normal. On an unknown date, Amylase: 42 international unit per litre. On an unknown date, Antinuclear antibody: (Negative) Negative. On an unknown date, Antithrombin III: revealed low activity at 50 % initially, but a repeat was negative. On an unknown date, Aspartate aminotransferase: 34 international unit per litre. On an unknown date, Blood alkaline phosphatase: 64 international unit per litre. On an unknown date, Blood bilirubin: 0.5 mg/dl. On an unknown date, Blood homocysteine: Normal. On an unknown date, Blood immunoglobulin G: (Negative) Negative. On an unknown date, Blood immunoglobulin M: (Negative) Negative. On an unknown date, Cardiolipin antibody: (Negative) Negative and (Negative) Negative. On an unknown date, Coagulation factor: Normal. On an unknown date, Computerised tomogram: revealed resolution of previously found thrombosis. On an unknown date, Computerised tomogram abdomen: revealed evidence of thrombus in the portal vein and superior mesenteric vein along with a somewhat nodular contour of liver suggesting underlying chronic liver parenchymal disease. On an unknown date, Computerised tomogram pelvis: revealed evidence of thrombus in the portal vein and superior mesenteric vein along with a somewhat nodular contour of liver suggesting underlying chronic liver parenchymal disease. On an unknown date, Fibrin D dimer: less than 150 ng/mL, normal. On an unknown date, Full blood count: showed no abnormalities. On an unknown date, Hepatitis B virus test: (Negative) Negative. On an unknown date, Hepatitis C virus test: (Negative) Negative. On an unknown date, Lipase: 23 international unit per litre. On an unknown date, Liver function test: Normal. On an unknown date, Magnetic resonance imaging abdominal: revealed a similar nonocclusive thrombus within the main portal vein extending into the proximal aspects of the right and left portal veins. The liver showed diffuse hepatic steatosis. On an unknown date, Metabolic function test: Normal. On an unknown date, Physical examination: normotensive with a normal heart rate and was afebrile. Patient was in distress with pain and had epigastric tenderness on abdominal palpation. On an unknown date, Protein C: Normal. On an unknown date, Protein S: Normal. On an unknown date, Prothrombin time: (Negative) gene mutation was negative. On an unknown date, Serum ferritin: Unremarkable 239 ng/mL.     The action taken with mRNA-1273 (Spikevax) (Unknown) was unknown.   For mRNA-1273 (Spikevax) (Unknown), the reporter considered PORTAL VEIN THROMBOSIS (Portal vein thrombosis) to be related.    The patient presented to the emergency department with complaints of severe upper abdominal pain that started one day after receiving first dose of Moderna vaccine.  Patient denied fever, chills, nausea, vomiting, chest pain, night sweats or weight loss. Patient did not have any significant history of coagulopathy in the past. The patient did not smoke, consume alcohol, or used any illicit drugs. The patient had no family history of clotting disorder.  There were no clinical signs and symptoms of active COVID-19 infection at that time and hence COVID PCR testing was not performed. Patient abdominal pain continued to improve and was currently maintained on apixaban 5 mg twice daily.  Company comment: This is a literature non-study case concerning a 51-year-old male patient with no relevant medical history, who was hospitalized due to the unexpected, serious (medically significant) adverse event of special interest of Portal vein thrombosis. The patient complained of severe upper abdominal pain 1 day after receiving the first dose of mRNA-1273 vaccine. On physical examination, the patient was in distress with pain and had epigastric tenderness on abdominal palpation. The rest of the physical examination and laboratory tests were unremarkable. Computed tomography (CT) of abdomen and pelvis at the emergency department revealed evidence of thrombus in the portal vein and superior mesenteric vein along with a somewhat nodular contour of liver suggesting underlying chronic liver parenchymal disease. This was followed by a magnetic resonance imaging (MRI) of the abdomen which revealed a similar non-occlusive thrombus within the main portal vein extending into the proximal aspects of the right and left portal veins. The liver showed diffuse hepatic steatosis. The patient was admitted and was started on heparin therapy during the hospital stay. He was discharged on apixaban 10 mg twice daily. He continued to follow up with hematologist. A follow up CT scan 3 months later revealed resolution of previously found thrombosis. His abdominal pain also continued to improve and is currently maintained on apixaban 5 mg twice daily. The benefit-risk relationship of mRNA-1273 is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 11-Aug-2022: Live follow-up received by safety on 11-Aug-2022, has Email received and contains significant information. Reporter information, Literature information, medical history, lab data, concomitant medications, treatment drugs and event details were updated.; Sender's Comments: This is a literature non-study case concerning a 51-year-old male patient with no relevant medical history, who was hospitalized due to the unexpected, serious (medically significant) adverse event of special interest of Portal vein thrombosis. The patient complained of severe upper abdominal pain 1 day after receiving the first dose of mRNA-1273 vaccine. On physical examination, the patient was in distress with pain and had epigastric tenderness on abdominal palpation. The rest of the physical examination and laboratory tests were unremarkable. Computed tomography (CT) of abdomen and pelvis at the emergency department revealed evidence of thrombus in the portal vein and superior mesenteric vein along with a somewhat nodular contour of liver suggesting underlying chronic liver parenchymal disease. This was followed by a magnetic resonance imaging (MRI) of the abdomen which revealed a similar non-occlusive thrombus within the main portal vein extending into the proximal aspects of the right and left portal veins. The liver showed diffuse hepatic steatosis. The patient was admitted and was started on heparin therapy during the hospital stay. He was discharged on apixaban 10 mg twice daily. He continued to follow up with hematologist. A follow up CT scan 3 months later revealed resolution of previously found thrombosis. His abdominal pain also continued to improve and is currently maintained on apixaban 5 mg twice daily. The benefit-risk relationship of mRNA-1273 is not affected by this report.