Background: Vaccination against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first approved on the 8th of December 2020. Though safe and effective, very rare side effects continue to be identified as global vaccination advances. They do not necessarily leave “a signal” in public registries if the incidence remains below previously reported total incidence levels. Optic neuritis (ON) is a rare but recognised adverse event after immunisation. The risk of post-vaccination ON and visual outcome in the context of global vaccination efforts against SARS-CoV-2 are not known. Methods: A global report on 73 deep-phenotyped individuals with post-SARS-CoV-2 vaccination ON observed in 15 of 55 countries with designated experts between 14 February to 18 July 2021. Statistical analyses were performed on type of vaccine, number of jabs, time to onset of ON, demographics, clinical features and treatment. Paraclinical data included immunological testing for autoantibodies against myelin oligodendrocyte glycoprotein (MOG) and aquaporin-4, magnetic resonance imaging (MRI) of the brain and orbits, retinal optical coherence tomography (OCT). The primary outcome was the visual acuity (VA). Findings: The characteristics of the 69 individuals included, differed from pre-COVID whole population-based incidence studies in frequency of bilateral presentation, age distribution and radiological features more commonly found in immune-mediated ON. Most events (67%) occurred after vaccination with AstraZeneca, followed by Pfizer-BioNTech (26%) and Sinovac (7%). In 56 this was after the first and in 13 after the second jab with the same vaccine. Autoantibodies against MOG were present in 15 and not detected for aquaporin-4. The condition was steroid responsive in most (58/62), requiring plasma exchange in a few (5) with spontaneous recovery in the remainder (7). The incidence was highest in the UK (0.036 per 100,000 persons) where vaccination commenced earliest. Importantly, the pattern of presentation in time lagged about 1-5 weeks behind the pattern of national age group vaccination. The median VA at presentation was logMAR 1.0 and recovered to 0.0. Interpretation: Post-SARS-CoV-2 vaccination ON is an extremely rare adverse event with generally good outcome of visual function. The global incidence of post-vaccination ON (0.0017 per 100,000 persons) is lower than for ON (3.74 per 100,000 persons in the UK). A causal relationship is plausible, but the overall risk benefit balance is in favour of SARS-CoV-2 vaccination. Funding Information: None. Declaration of Interests: None. Ethics Approval Statement: Reporting of patients was approved by the Institutional Research Board at Moorfields Eye Hospital (study number CaRS_24).

An association between varicella zoster virus (VZV) and multiple sclerosis (MS) has been reported in Mexican populations. The aim of this study was to compare the response of T cells from MS patients, during relapse and remission, to in vitro stimulation with VZV, adenovirus (AV) and Epstein–Barr virus (EBV). Proliferation and cytokine secretion of T cells from 29 relapsing-remitting MS patients and 38 healthy controls (HC) were analyzed by flow cytometry after stimulating with VZV, AV or EBV. IgG and IgM levels against VZV and EBV were quantified using Enzyme-Linked Immunosorbent Assay. Relapsing MS patients showed a higher percentage of responding CD4+ and CD8+ T cells against VZV compared to AV. In HC and remitting MS patients, proliferation of CD4+ T cells was higher when stimulated with VZV as compared to EBV. Moreover, T cells isolated from remitting patients secreted predominantly Th1 cytokines when cell cultures were stimulated with VZV. Finally, high concentration of anti-VZV IgG was found in sera from patients and controls. The results support previous studies of an VZV-MS association in the particular population studied and provide additional information about the possible role of this virus in the pathogenesis of MS.

Background: Anti-NMDA receptor encephalitis is an autoimmune disease characterized by severe neuropsychiatric disturbances, often misdiagnosed as a primary psychiatric disorder. Early diagnosis is crucial, as delayed immunotherapy is associated with worse outcomes. Electroencephalography (EEG) is a widely available tool for detecting abnormalities that may aid in early detection of cases that should undergo a thorough approach. Although EEG has high sensitivity, its specificity remains a challenge. Methods: This case-control study was carried out in the National Institute of Neurology and Neurosurgery of Mexico and included 241 patients with acute or subacute neuropsychiatric disturbances, raising the suspicion of autoimmune encephalitis and leading to the determination of NMDA receptor antibodies in the cerebrospinal fluid (CSF). EEG patterns were analyzed to determine the frequency of abnormal findings and their diagnostic value. Results: 140 patients were diagnosed as having definite anti-NMDA receptor encephalitis, whereas 101 had a negative determination of NMDA receptor antibodies. Psychosis was very frequent in both groups. However, severe cognitive dysfunction and catatonia were significantly more frequent in anti-NMDA receptor encephalitis patients. EEG abnormalities were significantly more frequent in patients with anti-NMDA receptor encephalitis patients (87.2% vs. 61.2%, p < 0.001). Diffuse slowing (75.7% vs. 46.6%, p < 0.001) and the extreme delta brush pattern (8.8% vs. 0%, OR = 20.6, p = 0.002) were significantly associated with anti-NMDA receptor encephalitis. Logistic regression analysis confirmed that an abnormal EEG remained strongly associated with anti-NMDA receptor encephalitis after adjusting for confounders. Conclusions: EEG abnormalities, particularly diffuse slowing and the extreme delta brush pattern, provide important diagnostic clues in patients with a clinical suspicion of anti-NMDA receptor encephalitis. While EEG has high sensitivity, its specificity is enhanced by recognizing distinct patterns. These findings support the integration of EEG into diagnostic algorithms to guide early detection and management of autoimmune encephalitis.