Introduction: Recent studies suggested that anti-CD20 and fingolimod may be associated with lower anti-spike protein-based immunoglobulin-G response following COVID-19 vaccination. We evaluated if COVID-19 occurred despite vaccination among patients with multiple sclerosis (MS) and neuromyelitis optica (NMO), using the COVISEP registry. Case series: We report 18 cases of COVID-19 after two doses of BNT162b2-vaccination, 13 of which treated with anti-CD20 and four with fingolimod. COVID-19 severity was mild. Discussion: These results reinforce the recommendation for a third COVID-19 vaccine dose among anti-CD20 treated patients and stress the need for a prospective clinical and biological study on COVID-19 vaccine efficacy among MS and NMO patients.