Impaired humoral and cellular response to BNT162b2 in patients with MM. (A) Flowchart of the study. BNT162b2 anti–SARS-CoV-2 vaccine was used in this study; 2 doses were administrated 4 weeks apart. In all, 16 patients (from the anti-CD38 group) received a third booster vaccine dose. The anti-CD38 group is defined as patients who were treated with anti-CD38 immunotherapy. The convalescent group is defined as patients with a history of SARS-CoV-2 infection who were given the vaccine. T0 is the time before vaccine, M1 is 1 month after the first vaccine dose, and M3 is 3 months after the first vaccine dose. (B-C) SARS-CoV-2–specific IgG and IgA production quantified by S-Flow in 60 patients with MM who had never been infected with SARS-CoV-2 and 23 healthy volunteers. (B) IgG (left panel) and IgA (right panel) quantification in controls or patients with MM before vaccination (T0) and at M1 and M3. (C) Comparison of IgG amounts in patients with MM who were treated or not treated with anti-CD38 immunotherapy. (D-E) Quantification of anti-SARS-CoV-2 nAbs against alpha or delta variants in controls (n = 23) or patients with MM (n = 60). (D) Comparison between controls and patients with MM. (E) Comparison between patients receiving or not receiving anti-CD38 immunotherapy. (F) Quantification of cellular immune response by S1 or S2 EliSpot (in spot forming units, SFU, per 10⁶ CD3 cells) in controls (n = 21) or patients with MM (n = 26). Patients receiving anti-CD38 immunotherapies are indicated. Error bars represent standard error. *P < .05; **P < .01; ***P < .001; ****P < .0001. ns, not significant.