Portal vein thrombosis after second Pfizer/BioNTech vaccine; This is a literature report for the following literature source(s):   A 45-year-old never-smoker man with a body mass index of (BMI) 33 kg/m2, no other significant medical history, and no family history of coagulable disorders had presented with an 8-day history of gradually worsening upper abdominal pain, malaise, nausea, vomiting, and anorexia that had started several hours after his second Pfizer/BioNTech BNT162b2 COVID-19 vaccine. His platelet count was normal, the hematocrit was 45%, the blood urea nitrogen/creatinine ratio was 14, and he had tested negative for COVID-19 via a polymerase chain reaction test at admission. A computed tomography (CT) scan of the abdomen and pelvis with intravenous contrast revealed thrombosis of the superior mesenteric vein, main portal vein, and right portal vein and peripancreatic edema (his lipase and liver function test results were within normal limits). Before beginning anticoagulation therapy, blood was drawn to perform a thrombosis panel, which revealed protein C activity of 54% (normal range, 60%-150%) and antithrombin Ill activity of 79% (normal range, 92%-136%). The thrombosis panel results were otherwise negative (including for paroxysmal nocturnal hemoglobinuria and JAK2 mutations). His symptoms gradually improved with intravenous fluids and parenteral anticoagulation therapy (intravenous heparin, which was transitioned to enoxaparin) during his 3-day hospital stay. His creatinine remained stable, and his hematocrit at discharge was 44.9%. He was discharged with rivaroxaban (15 mg twice daily for the first 21 days and 20 mg daily thereafter). A contrast-enhanced CT scan performed 41 days after his second vaccine demonstrated continued thrombosis in the splenic, superior mesenteric, and portal veins, with new cavernous transformation and resolution of the peripancreatic edema. The liver function test and lipase results were normal at 45 days after the vaccine. A contrast-enhanced CT scan at 188 days after his second vaccine was notable for cavernous vein transformation. Rivaroxaban was discontinued after 6 months in accordance with the hematology recommendations from another healthcare system after noting the cavernous transformation and improvement in symptoms. At the 6-month follow-up visit with our team, he endorsed intermittent vague mild right upper quadrant discomfort but felt overall well. At his 12-month follow-up visit, his symptoms had completely resolved, and the follow-up antithrombin Ill activity level was 77% without rivaroxaban. We plan to monitor him with annual clinical follow-up examinations and will order imaging studies as needed.; Sender's Comments: Based on possible temporal association the causal association of suspect drug BNT162b2  and for the reported events -Portal vein thrombosis cannot be excluded. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.