Neuromyelitis optica; This literature-non-study case was reported in a literature article and describes the occurrence of NEUROMYELITIS OPTICA SPECTRUM DISORDER (Neuromyelitis optica) in a 19-year-old female patient who received mRNA-1273 (Spikevax) for COVID-19 prophylaxis.   No Medical History information was reported.   On an unknown date, the patient received dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date,  after starting mRNA-1273 (Spikevax), the patient experienced NEUROMYELITIS OPTICA SPECTRUM DISORDER (Neuromyelitis optica) (seriousness criteria hospitalization and medically significant). The patient was treated with METHYLPREDNISOLONE (intravenous) for Neuromyelitis optica, at an unspecified dose and frequency and RITUXIMAB (intravenous) for Neuromyelitis optica, at an unspecified dose and frequency. At the time of the report, NEUROMYELITIS OPTICA SPECTRUM DISORDER (Neuromyelitis optica) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Anti-aquaporin-4 antibody: (Negative) Negative. On an unknown date, Antibody test: (Negative) Negative. On an unknown date, CSF test: (Positive) Neutrophilic pleocytosis with increased IgG synthesis rate was observed.. On an unknown date, Electrocardiogram: Sinus tachycardia, MRC grade 3-4/ 5 power in the arms, 0/ 5 in the legs with approximately T4 sensory level were observed.. On an unknown date, Magnetic resonance imaging neck: T2 prolongation in the spinal cord extending from the cervicomedullary junction to the conus medullaris.   The action taken with mRNA-1273 (Spikevax) (Unknown) was unknown.   For mRNA-1273 (Spikevax) (Unknown), the reporter considered NEUROMYELITIS OPTICA SPECTRUM DISORDER (Neuromyelitis optica) to be related.    No concomitant medications were reported.  Patient experienced two days of progressive, severe weakness and sensory changes in the arms first and then in legs. next morning patient experienced urinary incontinence like symptoms. Patient was treated with high-dose of intravenous methylprednisolone, and rituximab. Patient received plasmapheresis therapy. Bilateral, saddle pulmonary emboli were discovered shortly after admission.  Company Comment: This is a literature non-study case concerning a 19-year-old female patient with no reported medical history, who was hospitalized due to the unexpected, serious (medically significant) adverse event of special interest of Neuromyelitis optica spectrum disorder. 15 days after receiving a dose of mRNA-1273 vaccine, the patient developed progressive severe weakness and sensory changes first in the arms then legs and with urinary incontinence. Examination revealed sinus tachycardia, MRC grade 3-4/5 power in the arms and 0/5 in the legs with approximately T4 sensory level. Cervical spine MRI revealed T2 prolongation in the spinal cord extending from the cervicomedullary junction to the conus medullaris. Cerebrospinal fluid analysis revealed neutrophilic pleocytosis with increased IgG synthesis rate and positive CSF antibody for aquaporin-4 (AQP4). Bilateral saddle pulmonary emboli were also discovered shortly after admission. The patient was treated with high-dose intravenous methylprednisolone, plasmapheresis and Rituximab. The outcome of the event was unknown at the time of the report. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This is a literature non-study case concerning a 19-year-old female patient with no reported medical history, who was hospitalized due to the unexpected, serious (medically significant) adverse event of special interest of Neuromyelitis optica spectrum disorder. 15 days after receiving a dose of mRNA-1273 vaccine, the patient developed progressive severe weakness and sensory changes first in the arms then legs and with urinary incontinence. Examination revealed sinus tachycardia, MRC grade 3-4/5 power in the arms and 0/5 in the legs with approximately T4 sensory level. Cervical spine MRI revealed T2 prolongation in the spinal cord extending from the cervicomedullary junction to the conus medullaris. Cerebrospinal fluid analysis revealed neutrophilic pleocytosis with increased IgG synthesis rate and positive CSF antibody for aquaporin-4 (AQP4). Bilateral saddle pulmonary emboli were also discovered shortly after admission. The patient was treated with high-dose intravenous methylprednisolone, plasmapheresis and Rituximab. The outcome of the event was unknown at the time of the report. The benefit-risk relationship of mRNA-1273 is not affected by this report.