SEVERE ACUTE HEMOLYTIC ANEMIA POST COVID VACCINATION; This is a literature report for the following literature source(s).  A 26-year-old female patient received COVID-19 Vaccine - Manufacturer Unknown, as dose 2, single (Batch/Lot number: unknown) for covid-19 immunisation. The patient's relevant medical history included: "warm autoimmune hemolytic anemia" (unspecified if ongoing); "immune thrombocytopenia" (unspecified if ongoing); "triple positive antiphospholipid syndrome" (unspecified if ongoing); "chronic migraine" (unspecified if ongoing). The patient's concomitant medications were not reported. Vaccination history included: Covid-19 vaccine (DOSE 1 SINGLE), for covid-19 immunization. The following information was reported: HAEMOLYTIC ANAEMIA (hospitalization, medically significant, life threatening), outcome "recovering", described as "SEVERE ACUTE HEMOLYTIC ANEMIA POST COVID VACCINATION". The patient underwent the following laboratory tests and procedures: Haemoglobin (9-10.5): 4.3 g/dl, notes: severelyanemic/decreased; 3.3 g/dl, notes: decreased; 7.2 g/dl, notes: Increased. Therapeutic measures were taken as a result of haemolytic anaemia.  Clinical course: The patient presented to the emergency department with worsening generalized fatigue for one week associated with headache, dyspnea on exertion, nausea, vomiting and lightheadedness. Of note, she had received her second dose of mRNA COVID-19 vaccine 4 days prior to presentation. On admission, patient was found to be severely anemic with a hemoglobin of 4.3g/dL which is decreased from her baseline hemoglobin of 9-10.5g/dL; however, W-AIHA precluded the administration of blood product until adequate blood with the appropriate antibodies could be acquired. During the hospitalization, hemoglobin decreased to 3.3g/dL. Patient was then administered the most compatible blood product which she tolerated well. Hematology was consulted who started the patient on hydroxychloroquine, high dose methylprednisolone, and Intravenous Immunoglobulin (IVIG). Throughout the admission, the patient remained asymptomatic. After 2 days of IVIG, three days of high dose glucocorticoids, and one unit of packed red blood cells, the patient's hemoglobin increased to 7.2g/dL. Patient was discharged home on prednisone taper and hydroxychloroquine.  Conclusion(s): Episodes of hemolytic anemia after either the first or second dose of mRNA COVID vaccines are rare and have occurred in patients with known hematological pathology as well as patients without any history of hematologic or immunologic disorders. When taking the history of patients presenting with hemolytic anemia, it is important to query recent vaccinations as, while rare, mRNA COVID vaccine may well be the etiology. While this ultimately will likely not change patient management, this information would be beneficial for further study.; Sender's Comments: Based on the information provided in the narrative, a causal association between the event Haemolytic Anaemia and the suspect drug cannot be completely 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.