SEVERE THROMBOCYTOPENIA; ACUTE RIGHT MCA INFARCT; CEREBRAL EDEMA; HEMORRHAGIC TRANSFORMATION; ARTERIAL THROMBOSIS; VENOUS THROMBOSIS; SUSPECTED IMMUNOLOGICAL VACCINE FAILURE; This spontaneous report was received from literature: This report concerned a 37 year old female of an unspecified race and ethnic origin.  The objective of this study was to describe, surfacing of rare severe thrombotic complications associated with thrombocytopenia within the first 3 weeks of  vaccine. The patient's height, and weight were not reported. The patient's concurrent conditions included: migraines, and the patient received oral contraceptives. The patient received Covid-19 vaccine  (suspension for injection, route of admin, and batch number were not reported) dose, start therapy date were not reported, 1 total, administered for prophylactic vaccination. The batch number was not reported and has been requested. No concomitant medications were reported.  On an unspecified date, 10 days post vaccination, the patient experienced acute onset of headache, dense left-sided hemiparesis with hemineglect and right gaze deviation. The  Stroke Scale was 15. Acute computer tomography (CT) angiogram of head and neck showed occlusion of the right internal carotid artery terminus, segmental occlusions of the right middle cerebral artery (M1) and anterior cerebral arteries (A1 and A2). On head CT, the Alberta Stroke Program Early CT Score (ASPECTS) was 9. Intravenous tPA (Alteplase) was not administered given unknown last known well. The patient underwent mechanical thrombectomy, where modified treatment in cerebral ischemia (mTICI) score 2b recanalization was achieved after two passes. Brain MRI post-thrombectomy demonstrated an acute right middle cerebral artery (MCA) infarct with associated edema and hemorrhagic transformation. On admission (hospitalization), the platelet count was 121000/ul (reference range: 150-400000/ul) and rapidly declined reaching a nadir of 30000/ul within the next 24 h. A peripheral blood smear confirmed thrombocytopenia and rare schistocytes. Additional studies showed elevated d-dimer level (2960 ng/ml, peaking at over 40,000 ng/ml; reference range: <230ng/ml) normal international normalised ratio (INR), partial thromboplastin time (PTT), and fibrinogen. SARS-CoV-2 RNA was not detected on reverse-transcriptase polymerase-chain-reaction assay of nasopharyngeal swab. SARS-CoV-2 IgM/IgG was negative (suspected immunological vaccine failure). Doppler ultrasound revealed right common femoral vein partially occlusive thrombosis, acute deep vein thrombosis of the left brachial vein and bilateral cephalic veins. A transthoracic echocardiogram was negative for right-to-left shunt. Other testing included negative HemosIL Heparin-induced Thrombocytopenia platelet factor 4 antibody (HTI-Ab (PF4-H)) assay, factor V Leiden, prothrombin gene mutation, non-reactive hepatitis, human immunodeficiency virus (HIV), syphilis panels, antinuclear antibody (ANA), antineutrophil cytoplasmic antibody (ANCA), and double stranded DNA antibody (dsDNA) antibodies. Given the rapid onset of concurrent arterial and venous thrombosis, there was suspicion for catastrophic antiphospholipid syndrome, however, anti-cardiolipin, anti-B2 glycoprotein and lupus anticoagulant were negative. The patient was empirically treated with two doses of intravenous immune globulin (IVIG) 1 gr/Kg (for 50 kg) and pulse intravenous (IV) dexamethasone 40mg for 4 days. Worsening midline shift on imaging and clinical deterioration prompted urgent decompression hemicraniectomy. The treatment with IVIG was followed by relative platelet count stabilization during a 7-day period. The enzyme-linked immunosorbent assay for antibodies against PF4 came back positive (1.986 optical-density units; normal range reference, 0.300), and argatroban drip was started (therapeutic target of 1.5 x base PTT). The action taken with Covid-19 vaccine  was not applicable. The outcome of the severe thrombocytopenia, acute right MCA infarct, venous thrombosis, arterial thrombosis, suspected immunological vaccine failure, cerebral edema, and hemorrhagic transformation was not reported. The authors concluded, high index of suspicion in recently vaccinated people for COVID-19 and rapid recognition of VITT (which should include an approved PF4 ELISA) has important relevance for optimal management1 involving: IVIG,5 high-dose glucocorticoids, non-heparin anticoagulants and avoiding platelet transfusion (given the consumptive nature of this thrombotic phenomenon). This report was serious (Hospitalization Caused / Prolonged, and Other Medically Important Condition).; Sender's Comments: V0: 20210957986-Covid-19 vaccine -arterial thrombosis, venous thrombosis, severe thrombocytopenia. This event(s) is labeled per  and is therefore considered potentially related.  20210957986-Covid-19 vaccine ad26.cov2.s-acute right MCA infarct, cerebral edema, and hemorrhagic transformation. This event(s) is considered unassessable. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event(s).  20210957986-Covid-19 vaccine ad26.cov2.s-suspected immunological vaccine failure. This event(s) is considered not related. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There are other factors more likely to be associated with the event(s) than the drug. Specifically: SPECIAL SITUATIONS