diagnosis of neuromyelitis optic spectrum disorder (NMOSD)-optic neuritis; diagnosis of neuromyelitis optic spectrum disorder (NMOSD)-optic neuritis; This is a literature report.  A 43-year-old female patient received BNT162b2 (BNT162B2), as dose 1, single (Batch/Lot number: unknown) for covid-19 immunisation. The patient's relevant medical history included: "type 2 diabetes mellitus" (unspecified if ongoing), notes: medically-controlled; "arterial hypertension" (unspecified if ongoing), notes: medically-controlled; "secondary hypothyroidism" (unspecified if ongoing), notes: medically-controlled; "secondary hypothyroidism" (unspecified if ongoing); "migraine headaches" (unspecified if ongoing). The patient's concomitant medications were not reported. Past drug history included: Iodine for Graves disease, notes: following radioactive iodine treatment. The following information was reported: NEUROMYELITIS OPTICA SPECTRUM DISORDER (hospitalization, medically significant), OPTIC NEURITIS (hospitalization, medically significant), all with latency 2 days after the suspect product(s) administration, outcome "recovering" and all described as "diagnosis of neuromyelitis optic spectrum disorder (NMOSD)-optic neuritis". A woman with a history of medically-controlled type 2 diabetes mellitus, arterial hypertension, secondary hypothyroidism following radioactive iodine treatment for Graves disease, and migraine headaches experienced flashing lights in the right eye associated with a frontal headache that was phenotypically distinct from her usual migraines. Four days later she awoke with blurred vision in the right eye associated with painful eye movement. The next day she was examined by a general ophthalmologist who noted a visual acuity of 20/40 in the right eye and 20/20 in the left eye, with a right relative afferent pupillary defect (RAPD). The remainder of the examination, including the fundus, was normal. Macular optical coherence tomography (OCT) was normal. The peripapillary retinal nerve fiber layer (pRNFL) thickness was 132 micrometer in the right eye and 123 micrometer in the left eye That evening after visiting with the ophthalmologist, magnetic resonance imaging (MRI) of the brain and orbits with contrast demonstrated enhancement of both optic nerve sheaths, with the remainder of the brain appearing normal. Two days later she noted dark vision in the left eye associated with painful eye movements and continued visual decline in the right eye. Visual acuity measured as \ counting fingers in each eye. She was admitted to the hospital. CBC, CMP, erythrocyte sedimentation rate, C-reactive protein, antinuclear antibodies, antineutrophil cytoplasmic antibodies, angiotensin-converting enzyme, human immunodeficiency virus antigen, and antibodies to Treponema pallidum, Borrelia burgdorferi, and Bartonella henselae antibodies were all negative or normal. Live cell-based assay for myelin oligodendrocyte glycoprotein (MOG) immunoglobulin G (IgG) and aquaporin-4 (AQP-4) IgG were eventually reported to be negative (the results were not immediately available). Cerebrospinal fluid (CSF) analysis revealed 6/uL white blood cells (96% lymphocytes), 0/uL red blood cells, 113 mg/dL glucose, 23 mg/dL protein, non-reactive VDRL, negative cytology and absent oligoclonal bands. Whole body fluorodeoxyglucose (FDG) positron emission tomography (PET)-computed tomography (CT) was normal. Prior to obtaining the AQP-4 IgG results, she was given a presumptive diagnosis of neuromyelitis optic spectrum disorder (NMOSD)-optic neuritis and treated as such with 3 consecutive days of intravenous (IV) methylprednisolone (1 gram/day) and 7 treatments of plasma exchange (PLEX). Subjectively she started noticing improvement in vision after the last PLEX treatment. During hospitalization, she informed the medical team that 6 days prior to the onset of her initial symptoms (10 days prior to the visual loss right eye) she had received the first dose of the Pfizer-BioNTech coronavirus disease 2019 (COVID- 19) vaccine. Four weeks later, vision had subjectively improved slightly in both eyes, but 8 weeks later visual acuity returned to 20/20 in each eye, with optic disc pallor, inferior visual field defects, and pRNFL thinning. As per Macular optical coherence tomography (OCT) found peripapillary retinal nerve fiber layer thickness printout (69 u right eye and 74 u left eye). 2 months after presentation. In Fundus photographs found normal appearing optic discs in both eyes. In visual field test, found bilateral inferior visual field defects more pronounced in the right eye, 2 months after presentation. Approximately 16 months later, vision was stable at 20/20 in each eye, with minor inferior visual field defects, more obvious optic disc pallor, and further pRNFL thinning. As per Macular optical coherence tomography (OCT) found peripapillary retinal nerve fiber layer thickness printout (48 u right eye and 53 u left eye), approximately 16 months after presentation. In fundus photographs found bilateral optic disc pallor, approximately 16 months after presentation. Static perimetry showing bilateral inferior visual field defects, right eye slightly worse compared to left eye, approximately 16 months after presentation. She declined any further COVID-19 vaccination injections.; Sender's Comments: Based on the current available limited information in the case provided, the causal association between the events Neuromyelitis Optica spectrum disorder and Optic Neuritis and the use of suspect product cannot be fully excluded. The impact of this report on the benefit-risk profile of the Pfizer product and on the conduct of the study 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.