S1PR1 and myeloid sarcoma: Considering that MS is an autoimmune disease whose pathology can be explained by an altered immune system [6], and that some DMTs, especially CD20 depleting agents such as ocrelizumab and sphingosine-1-phosphate receptor modulator (S1PRM) such as fingolimod, seem to be able to decrease the antibody response against COVID-19 vaccines [7], and given the collection of new data among our MS patients, we carried out this retrospective study with the aim to evaluate the safety in terms of AEFI occurrence and the antibody response after the third dose of COVID-19 vaccines in people with MS.