The allele frequencies of HLA-DRB1*15 were 17.6% and 22.2% in control groups 1 and 2, respectively, but none of the patients with a new diagnosis of MS post-COVID-19 vaccine resulted in HLA-DRB1*15 at least in one of the two alleles, while HLA-DRB1*08pos and HLA-DRB1*10pos MS patients were present only in the subgroup of our cohort with a vaccine-related disease onset (Figure 4). This evidence concerns the gene HLA-DRB1 and myeloid sarcoma.