This case was reported in a literature article and described the occurrence of neuromyelitis optica spectrum disorder in a adult subject who received Flu vaccine unspecified for prophylaxis. Concurrent medical conditions included neuromyelitis optica spectrum disorder. On an unknown date, 40 days after receiving Flu vaccine unspecified, the subject developed neuromyelitis optica spectrum disorder. Serious criteria included GSK medically significant. Additional event(s) included optic neuritis with serious criteria of GSK medically significant and condition aggravated. The outcome of neuromyelitis optica spectrum disorder was recovered/resolved. The outcome(s) of the additional event(s) included optic neuritis (recovered/resolved) and condition aggravated (recovered/resolved). The investigator considered that there was a reasonable possibility that the neuromyelitis optica spectrum disorder, optic neuritis and condition aggravated may have been caused by Flu vaccine unspecified. Relevant Tests: Lab tests were performed on unspecified date. Expanded Disability Status Scale (EDSS)  from baseline to nadir was 3.0. AQP-4 serostatus was positive. Additional information was provided. This case was reported in a literature article and described the worsening of neuromyelitis optica spectrum disorder (NMOSD) and optic neuritis (ON) in a patient aged 38.4 and 60-year of unspecified gender who was vaccinated with unspecified inactivated influenza vaccine (manufacturer unknown) for prophylaxis. This case corresponds to number 10 of table 2 in this literature article. The patient was a part of retrospective analysis that investigated the association of a relapse occurring within 30, 60, and 90 days of a vaccination and compared it with the association of a relapse occurring within randomly selected dates. The goal was to determine if vaccines may increase the risk of a Neuromyelitis optica spectrum disorder (NMOSD) relapse conducted at three NMOSD centers world-wide. The patient had concurrent condition of NMOSD and was not on immunotherapy at the time of vaccination. No information on patient's family or medical history or concomitant medication was provided. On 30 September 2012, the patient received unspecified inactivated influenza vaccine intramuscularly (administration site unspecified; dosages unknown; batch number not provided). Age of vaccination was not provided. On an unspecified date, 40 days after vaccination, the patient experienced worsening of NMOSD and optic neuritis. [In this study, relapses were defined across all centers as a new or worsening acute neurologic symptom lasting at least 24 h, associated with a change in exam localizing to the central nervous system (CNS) and not explainable by fever, infection or metabolic condition. Magnetic resonance imaging (MRI) was used for relapse confirmation as needed. Relapse severity was characterized by net change in the Expanded Disability Status Scale (EDSS) from baseline to nadir]. EDSS from baseline to nadir was 3.0. AQP-4 serostatus was positive. In this study, the duration of disease was 3.1 and 10.8 years. Treatment was unknown. The outcome of the event was not reported. The author considered the event of worsening of NMOSD and optic neuritis temporally associated with unspecified influenza vaccine. The author concluded, "comprehensive, well-controlled prospective analysis that assesses relapses, vaccines and infections would be warranted for future research to confirm our findings that suggest that patients who are treated with preventive immune suppression and receive routine vaccinations for common infections may fare better than those who do not." The article corresponding to this case is not available for regulatory submission due to copyright restriction. This is 1 of 13 valid cases reported in the same literature article. Lab Comments: Lab tests were performed on unspecified date. Expanded Disability Status Scale (EDSS) from baseline to nadir was 3.0. AQP-4 serostatus was positive.