BLOODY DIARRHEA; PLATELET COUNT DECREASED; FLARE OF IMMUNE THROMBOCYTOPENIA; ABDOMINAL CRAMPS; This spontaneous report was received from literature:  COVID-19 vaccination associated severe immune thrombocytopenia. Medical Journal. 2021 Jul 15;. This report concerned a 59 year old female. The patient's height, and weight were not reported. The patient's concurrent conditions included chronic immune thrombocytopenia (ITP), and systemic lupus erythematosus. The patient experienced flare of immune thrombocytopenia two years ago which was precipitated  by varicella zoster vaccine rge (cho) for prophylactic vaccination, and was treated successfully with steroids, following which her platelet count remained stable (~100 × 10*9/L). The patient received covid-19 vaccine ad26.cov2.s (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. Concomitant medications included hydroxychloroquine for systemic lupus erythematosus. On an unspecified date, the patient presented to emergency department for symptoms of abdominal cramps and bloody diarrhea that started 2 days after she had received the vaccine. The patient's physical exam was unremarkable. The patient was hospitalized (date and duration unspecified). Laboratory data (dates unspecified) included: Computerised tomogram abdomen (NR: not provided) showed mild distal colitis, and peripheral blood film (NR: not provided) did not show platelet clumping or schistocytes. The platelet count was 64 x 10*9/L on the day after the vaccination and subsequently dropped to 27 x 10*9/L the following day. Prior laboratory data showed non-reactive HIV and hepatitis B and C serology. Treatment medications (dates unspecified) included: dexamethasone and gradual improvement in platelet count was seen. The discussion included: vaccination associated ITP was a rare phenomenon. ITP after COVID19 vaccination was relatively a new occurrence, and the management and outcomes of these cases were not well published in medical literature. This report described case of severe ITP that occurred following vaccination and provided insights into the treatment and outcome for ITP secondary to covid-19 vaccination. The patient responded well to treatment with corticosteroids ± IVIG and if the treatment were not effective, and the platelet count remained very low, it would then be reasonable to escalate therapy to include a thrombopoietic agent and potentially vinca alkaloids depending upon response. Avoiding rituximab from initial treatment would be appropriate since the response to rituximab would take up to 68 weeks; furthermore, the response to COVID-19 vaccine may be impaired by rituximab. It remains uncertain whether post COVID-19 vaccination ITP cases will prove to be self-limiting or persist and lead to chronic ITP and also unclear if the ITP is secondary to the vaccination or primary ITP that was coincident with the vaccine. The clinical manifestation and the positive response to treatment akin to ITP, such as with corticosteroids ± IVIG, suggest an antibody-mediated platelet destruction. ITP has been previously reported with different types of vaccines including hepatitis B virus (HBV) human papilloma virus (HPV) varicella zoster, haemophilus infuenza, polio, pneumococcus, Diphtheria-tetanus-acellularpertussis (DTap) and measles-mumps rubella (MMR). Proposed mechanisms include molecular mimicry and antibody generation to adjuvants/additives included in the vaccine composition which can lead to generation of autoantibodies that cause platelet destruction and inhibit platelet production. Data also show that post-vaccination ITP ranges in severity from mild to moderate to severe and is highly responsive to IVIG treatment. Literature review shows conflicting data as some studies show evidence of ITP reactivation when exposed to the same vaccine while others do not demonstrate the ITP reactivation when the vaccine is repeated. Many authors believe that ITP is not an absolute contraindication for vaccination given a much higher rate of ITP linked with natural infection as compared to vaccination however recommend to avoid vaccination during active ITP flare. The conclusion included: As mass vaccination progresses, more data should be collected to establish a cause-effect relationship of COVID-19 vaccination and associated ITP so that guidelines could be formulated for safe administration for COVID-19 vaccination. This could be done by outlining possible contraindications and potential treatment measures for ITP so as to prevent fatal outcomes. Additionally, more research may be needed to make changes in vaccine composition to prevent thrombocytopenia. One consideration could be to monitor patients with history of ITP for an antibody response and reserving the second dose of the vaccine for those without an adequate response. Until there is further development of appropriate guidelines, physicians should discuss these risks and benefits. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient was recovering from platelet count decreased, and the outcome of abdominal cramps, bloody diarrhea and flare of immune thrombocytopenia was not reported. This report was serious (Hospitalization Caused / Prolonged).; Sender's Comments: V0:20210747155 -JANSSEN COVID-19 VACCINE Ad26.COV2.S-  bloody diarrhea,abdominal cramps, platelet count decreased ,flare of immune thrombocytopenia- 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: MEDICAL HISTORY, UNDERLYING DISEASE