SARS-CoV-2-specific IgG and ELISpot responses in 117 patients after hematopoietic stem cell transplantation (HSCT) and 35 healthy controls (HC), after two SARS-CoV-2 vaccinations. Panel (a) shows IgG antibody responses against SARS-CoV-2 spike (S) 1, (b) ELISpot responses to S antigens (S) and (c) to membrane (M) and nucleocapsid (NC). For comparison to these in house ELISpot assays (b,c), results of a commercial ELISpot, the T-SPOT.COVID (Oxford Immunotec, OI), are shown as panel (d). Parallel tests with both ELISpot formats were, performed in 17 patients and 13 healthy controls, respectively. Horizontal bold lines indicate median values, and dashed lines the cutoff for positive responses (antibody ratio of 1.1, 3 spots increment for in house ELISpot assays and 6 spots increment for the T-SPOT.COVID). S1-peptide mix of the SARS-CoV-2 spike (S) 1; S1/S2-peptide mix of the spike (S) 1 and S2; S Sino-S1 protein (Sino Biological); M-peptide mix of the membrane; NC-peptide mix of the nucleocapsid. ** p = 0.0002, *** p < 0.0001 (Mann–Whitney test).