ABSTRACT
Multiple myeloma (MM) patients may have a reduced response to vaccination due to immunodeficiency. The humoral and cellular response to SARS-CoV-2 mRNA full vaccination and booster dose as well as the impact of spike variants, including the emerging Omicron one, are still unclear and have been investigated in this study in a cohort of MM patients and those with pre-malignant monoclonal gammopathies. Firstly, we have shown that MM patients with relapsed-refractory disease (MMR) had a reduced spike-specific antibody levels and neutralizing titers after SARS-CoV-2 mRNA full vaccination. Interestingly, all the analyzed variants, remarkably Omicron, had a significant negative impact on the neutralizing ability of the vaccine-induced antibodies in all patients with MM and in smoldering MM too. Moreover, lower spike-specific IL-2-producing CD4+ T cells and reduced cytotoxic spike-specific IFN-{gamma} and TNF--producing-CD8+ T cells were found in MM patients as compared to MGUS. Finally, we found that booster immunization improved SARS-CoV-2 spike humoral and cellular responses in newly diagnosed MM (MMD) patients and in most, but not all, MMR patients. After the booster dose, a significant increase of the neutralizing antibody titers against almost all the analyzed variants was achieved in MMD. On the other hand, in MMR patients, Omicron retain a negative impact on neutralizing ability, suggesting these patients need to be considered still at risk of Omicron SARS-CoV-2 infection with a clinically relevant disease.