CD8A and myeloid sarcoma: In the absence of cross-reactive neutralising antibodies, CD8+ T cells form an important second line of protection as they recognise conserved viral peptides in emerging variants31–34 and ameliorate disease severity.20 35–37 Building upon the observation that some OCR-treated patients with MS displayed no antibody response to the SARS-CoV-2 mRNA vaccination regimen, we conducted a comprehensive analysis of the T cell compartments.