over several days she developed encephalopathy; over several days she developed visual hallucinations; over several days she developed transient auditory hallucination; Mild erythematous upper extremity rash; over several days she developed left-sided hemichorea; This is a literature report.  A 74-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: "anxiety" (unspecified if ongoing); "mild cognitive decline" (unspecified if ongoing). The patient's concomitant medications were not reported. Past drug history included: Covid-19 vaccine for COVID-19 immunisation, notes: Dose 1, single; manufacturer unknown.  The following information was reported: ENCEPHALOPATHY (medically significant), outcome "recovered", described as "over several days she developed encephalopathy"; HALLUCINATION, VISUAL (medically significant), outcome "unknown", described as "over several days she developed visual hallucinations"; HALLUCINATION, AUDITORY (medically significant), outcome "unknown", described as "over several days she developed transient auditory hallucination"; RASH ERYTHEMATOUS (non-serious), 6 weeks after the suspect product(s) administration, outcome "unknown", described as "Mild erythematous upper extremity rash"; CHOREA (non-serious), outcome "unknown", described as "over several days she developed left-sided hemichorea". The patient underwent the following laboratory tests and procedures: Autoantibody test: positive; Cardiolipin antibody: positive; negative after multiple repetitions; Electroencephalogram: unremarkable; Inflammatory marker test: normal; Negative, notes: neuronal autoantibodies; Serum: normal; Negative, notes: neuronal autoantibodies; Magnetic resonance imaging head: unremarkable; Positron emission tomogram: unremarkable; unremarkable. Therapeutic measures were taken as a result of encephalopathy, hallucination, visual, hallucination, auditory, rash erythematous, chorea.  Clinical course: The patient received her second dose of the primary COVID-19 mRNA vaccine series six weeks prior to symptom onset. One day prior to symptom onset she developed a mild erythematous upper extremity rash that was responsive to antibiotics. Over several days she developed left-sided hemichorea, encephalopathy, and transient auditory and visual hallucinations. Brain MRI, EEG, brain PET, and body PET-CT were unremarkable. Serum and CSF inflammatory markers were normal. Extensive and repeated serum and CSF testing for neuronal autoantibodies was negative. Serum autoantibody testing revealed only a positive anticardiolipin IgM, which was subsequently negative after multiple repetitions. She was empirically treated with 2 g/kg of IVIg and had near-complete resolution of her hemichorea and modest improvement in encephalopathy. Five months later she relapsed with an identical presentation and again received 2 g/kg of IVIg, which substantially decreased but did not fully resolve her hemichorea. She achieved remission following an outpatient course of methylprednisolone 750 mg IV weekly for nine weeks. Four months after treatment she relapsed again, this time achieving remission after repeated IV steroids and initiation of mycophenolate maintenance therapy.; Sender's Comments: Based on the information provided, and a temporal association, a causal association between reported events  encephalopathy, hallucination visual, hallucination auditory and suspect COVID-19 Vaccine - Manufacturer Unknown cannot be excluded.This 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 to regulatory authorities, Ethics Committees, and Investigators, as appropriate.