A Multicenter, Randomized, Controlled, Open-label, Group-Sequential, Phase 3 Study to Investigate the Efficacy, Safety, and Tolerability of Intravenous Gammagard Liquid (Immune Globulin Infusion, 10%) for Primary Infection Prophylaxis Compared With Secondary Infection Prophylaxis in Adult Subjects With Multiple Myeloma Receiving B-Cell Maturation AntigenxCD3-Directed Bispecific Antibody Therapy

Multiple myeloma is a cancer of the plasma cells in the bone marrow. The main aim of this study is to learn how well the Immune Globulin Infusion (human), 10 percentage (%) (IGI, 10%) can help prevent infections in participants with multiple myeloma receiving B-cell maturation antigen (BCMA) x cluster of differentiation 3 (CD3) directed bispecific antibody therapy. Participants will be randomly assigned to one of two groups: 1. Primary infection prevention group: They will receive IGI, 10% for 12 months. 2. Secondary infection prevention group: They will only receive IGI, 10% if they develop a serious infection during the 12 months study period. During the study, participants will visit their study clinic 15 times (for 4-week dosing interval) or 19 times (for 3-week dosing interval) and their total participation duration will be up to 14 months (including screening period approximately 8 weeks).

Biological: IGI, 10%