AQP4 and COVID-19: Regarding neuromyelitis optica spectrum disorders (NMOSD) two cases of manifestation with Aquaporin-4-antibody (AQP4) positive NMOSD after COVID-19 vaccination have been reported so far, one after application of the Oxford–AstraZeneca COVID-19 vaccine (AZD1222) and another case after vaccination with the Sputnik V COVID-19 vaccine (Gam-COVID-Vac), both viral vector vaccines [4, 5].