Immune response to vaccination. (A) Antibodies: RBD-specific end point enzyme-linked immunosorbent assay (ELISA) titer following COVID-19 mRNA vaccination: prior to vaccination and V2 following 2-dose vaccination series (24-103 days) (upper panel) is shown. Individual subject numbers are shown (3, 11, 12, and 16) for responders. RBD-specific ELISA titer stratified by treatment group; geometric mean titer (GMT) of responders is shown above the graph (lower panel). The limit of detection (LOD) is set at 50; samples below the LOD were given an arbitrary value of 49. Healthy subject samples were taken (13-28 days) following the 2-dose vaccination series (lower left panel). (B) RBD-specific memory B-cell frequency per 10⁶ peripheral blood mononuclear cells (PBMCs) following COVID-19 mRNA vaccination: prior to vaccination and V2 (24-103 days) following the 2-dose vaccination series (upper panel). Only subject 12 developed an MBC response. RBD-specific MBC frequency stratified by treatment group (lower panel). Geometric mean titer of responders is shown above the graph. Healthy subject samples (247-264) post 2-dose vaccine series are included (lower right panel). LOD = 0.1; an arbitrary number (0.08) was assigned to samples below the LOD. (C) S-specific CD4 (left upper panel) and CD8 (right upper panel) T-cell frequency per 10⁶ T cells following COVID-19 mRNA vaccination: prior to vaccination and V2 following 2-dose vaccination series (24-103 days) (lowerpanel). S-specific CD4⁺ and CD8⁺ response to vaccination: the increase in T-cell expansion from baseline, stratified by treatment group (lower panel). Geometric mean titer of responders is shown above the graph. LOD = 10; for subjects without a vaccine-specific response, an arbitrary value between 1.1 and 1.5 was assigned. (D) Humoral immune recall response to a childhood antigen (measles) in subjects with CLL and age/sex-matched healthy controls. Antibodies: measles-specific end point ELISA titer stratified by treatment group (left panel). LOD = 100; samples below the LOD were assigned an arbitrary value of 80. Geometric mean titer of responders is shown above the graph for each group. Memory B cells: measles-specific MBC frequency stratified by treatment group (right panel). Geometric mean frequency of responders is shown above the graph. LOD = 0.1; an arbitrary number between .05 and .1 was assigned to those samples. Red, active treatment; blue, observation after treatment; green, treatment naive; yellow, healthy age/sex-matched controls.