Immune thrombocytopenic purpura; This is a literature report.  A 77-year-old female patient received bnt162b2, bnt162b2 omi ba.4-5 (BNT162B2, BNT162B2 OMI BA.4-5), as dose 4 (booster), single (Batch/Lot number: unknown) for covid-19 immunisation. The patient's relevant medical history included: "hypertension" (unspecified if ongoing); "Hashimoto thyroiditis" (unspecified if ongoing); "Raynaud's syndrome" (unspecified if ongoing); "hematemesis" (unspecified if ongoing); "septic arthritis" (unspecified if ongoing); "hospitalization" (unspecified if ongoing), notes: for septic arthritis. The patient's concomitant medications were not reported. Vaccination history included: Moderna (DOSE 1, SINGLE), for COVID-19 immunisation; Moderna (DOSE 2, SINGLE), for COVID-19 immunisation; Moderna (DOSE 3 (BOOSTER), SINGLE), for COVID-19 immunisation. The following information was reported: THROMBOSIS WITH THROMBOCYTOPENIA SYNDROME (hospitalization, medically significant, life threatening), 56 hrs after the suspect product(s) administration, outcome "recovered", described as "Immune thrombocytopenic purpura". The patient underwent the following laboratory tests and procedures: Haemoglobin: 7.7, notes: units: M/uL; Further testing: did not support hemolytic anemia,, notes: infection including hepatitis, HIV, folate deficiency, vaccine induced thrombotic thrombocytopenia or heparin induced thrombocytopenia; Platelet count: 211 x10 3/mm3, notes: normal; less than 2; low at 6; 540 x10 3/mm3, notes: on the day of discharge; Smear test: no platelet clumping or schistocytes. Therapeutic measures were taken as a result of thrombosis with thrombocytopenia syndrome.  Clinical course details: A 77-year-old female with a history of hypertension, Hashimoto thyroiditis and Raynaud's syndrome presented with hematemesis. She was recently discharged after a two-week hospitalization for septic arthritis. The day before discharge, she received a Pfizer-BioNTech COVID-19 Bivalent (Original and Omicron BA.4/BA.5) vaccine, her 4th immunization after three Moderna Sars-CoV-2 mRNA vaccines with a pre-vaccine platelet count of 211 K/uL.She was hemodynamically stable on admission with widespread petechiae. Labs on admission revealed hemoglobin 7.7 M/uL and platelets less than 2 K/uL, without leukocytosis or bandemia. Peripheral smear had no platelet clumping or schistocytes. Further testing did not support hemolytic anemia, infection including hepatitis, HIV, folate deficiency, vaccine induced thrombocytopenia or heparin induced thrombocytopenia. The patient was transfused 4 units of platelets but platelet count remained low at 6 K/uL, without further bleeding episodes. She received intravenous immunoglobulin (IVIG) with dexamethasone for two days. Her platelet counts steadily increased, reaching 540 K/uL on the day of discharge. The patient developed acute thrombocytopenia approximately 56 hours post vaccination with a normal pre-vaccination platelet count. The first line treatment is IVIG and steroid, avoiding platelet transfusion. Recent literature has pointed out the possibility of COVID 19 vaccine induced ITP with univalent COVID 19 vaccines. Vaccine-induced ITP typically occurs 7-10 days after vaccination. Although, within 6 days of vaccination, the adjusted risk ratio of developing ITP with a ChAdOx1 mRNA vaccine was 3 times greater for vaccinated versus unvaccinated. This patient did not develop thrombocytopenia with three prior COVID-19 vaccines, but had acute thrombocytopenia with the Omicron mRNA vaccine. Previous studies have noted limitations in ruling the incidental ITP due to not having pre-vaccination platelet counts or in ruling out other causes of ITP. This case demonstrates a clear clinical progression of VITP with a documented normal pre-vaccine platelet count and subsequent work up that did not support other etiologies of thrombocytopenia. Prior to COVID-19, it was rare to see VITP in adults with a 'killed' vaccine. However, with the current robust mRNA bivalent COVID-19 vaccination campaign, we may see more ITP cases related to mRNA vaccine administration. Further research to identify risk factors for development of VITP may permit for appropriate monitoring/intervention, in efforts to decrease morbidity from this rare complication of COVID-19 vaccination.; Sender's Comments: Based on current information available the causal association between the event THROMBOSIS WITH THROMBOCYTOPENIA SYNDROME and suspect drug BNT162B2 cannot be excluded completely. 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.