Acquisition of anti-SARS-CoV-2 IgG after vaccination in patients with malignant lymphoma. (A) Anti-SARS-CoV-2 IgG titers increased after the first and second vaccine doses in healthy volunteers (blue dots) and patients in treatment for malignant lymphoma (red dots). Patients in treatment were defined as those receiving treatment at the time of the first dose or within 3 months after the last dose of medication. (B) Differences in antibody titers after the second dose in patients with B-cell malignancies who were in treatment regimens including anti-CD20 antibody therapeutics. IgG titers after the second dose in the same group with appropriate laboratory data were stratified according to the respective cutoff values of prevaccination peripheral blood CD19⁺ cell count (20 cells per microliter) (C), peripheral blood CD4⁺cell count (320 cells per microliter μL) (D), and serum IgM level (20 mg/dL) (E), respectively. The cutoff values were calculated by analysis of the receiver operating characteristic curve shown in supplemental Figure 3. pre, before vaccination; adm, administration; treatment start-3M, patients under therapy or up to 3 months after completion of the treatment regimen.