Background Vaccination is a recognised trigger of ADEM and approximately 50% paediatric cases have antibodies to MOG. The SARS-CoV-2 mass vaccination programme could therefore trigger cases of MOGAD. Neuromyelitis optica (NMO) is an autoimmune inflammatory condition of the CNS associ- ated with antibodies to AQP4.

Method Ten patients (ages 22 – 65 years) with antibodies to MOG or AQP4 were referred to the NHS England NMO service having developed acute onset CNS inflammation within 8 weeks of vaccination.

Results Eight patients had MOGAD, seven of whom received the AstraZeneca vaccine (AZV) and one the Pfizer vaccine (PV). Only the post-PV MOGAD patient presented with typical adult-onset phenotype of isolated ON. All post-AZV MOGAD patients presented atypically; 85.7% had LETM and 71.4% had intrac- erebral lesions, resembling ADEM more commonly seen in paediatric MOGAD. The atypical presentation supports a causative role of AZV, but the role of PV is less convincing.

Two patients had AQP4-NMOSD with typical demographic features. Both received AZV. Less typically, one young adult presented with LETM rather than characteristic young adult ON, the other had a silent short segment myelitis, which is rarely seen in AQP4-NMOSD. Both patients achieved good outcomes.

Conclusion We discuss the potential causation and pathophysiological mechanisms.