Patients with kidney failure are at increased risk during the COVID-19 pandemic and effective vaccinations are needed . It is not known how efficient mRNA vaccines mount B and plasma cell responses in dialysis patients (DP) or kidney transplant recipients (KTR) compared to healthy controls (HC). We studied humoral and B cell responses of 25 HC , 44 DP and 40 KTR . Markedly impaired anti-BNT162b2 responses were identified among KTR and DP compared to 100% seroconversion in HC . In DP, the response was delayed (3-4 weeks after boost) and reduced with anti-S1 IgG positivity in 31 (70.5 %) and anti-S1 IgA in 30 (68.2 %) of 44, respectively . In contrast, KTR did not develop IgG response except one patient who had prior unrecognized infection and developed anti-S1 IgG . The majority of antigen-specific B cells (RBD+) were identified in the plasmablast or post-switch memory B cell compartments in HC, whereas these RBD+ B cells were enriched among pre-switch and naive B cells from DP and KTR . Single cell transcriptome and CITE-seq analyses found reduced frequencies of plasmablasts, TCF7+CD27+GZMK+ T cells and proliferating MKI67-expressing lymphocytes among KTR non-responders . Importantly, the frequency and absolute number of antigen-specific circulating plasmablasts in the whole cohort correlated with the Ig response, a characteristic not reported for other vaccinations . In conclusion, this data indicate that lack of T cell help related to immunosuppression results in impaired germinal center differentiation of B and plasma cell memory . There is an urgent need to improve vaccination protocols in patients after kidney transplantation or on chronic dialysis.