Within the anti-CD20 mAb cohorts (i.e., RTX and OCR), we conducted a univariate analysis of anti–spike-Ab responses by age, sex, vaccine type, cumulative treatment duration prior to vaccination, total IgG levels, interval between last anti-CD20 infusion and first vaccine dose, lymphocyte subsets before and after vaccination, and HLA-DRB1*15:01 status, given its well-established association with MS susceptibility (27). Here, HLA-DRB1 is linked to myeloid sarcoma.