Role of Antibiotic Therapy or Immunoglobulin On iNfections in hAematoLogy Immunoglobulin Stopping or Extension (Stop Ig)

This study is being conducted to find out how safe and effective different strategies of infection prevention are in comparison to each other, for preventing infection in patients with blood cancers. The best way to find out this information is to directly compare the effect of different treatment strategies in patients with blood cancers. We want to know how these different treatments impact on your health and your use of healthcare services. This research project uses an Adaptive Platform Design. This design allows the researchers to compare multiple infection prevention strategies within the same trial at the same time (rather than running separate trials), to analyse results as the trial occurs and to add new research questions during the course of the trial. The treatments that you may receive as part of the study will be determined by which domain(s) of the platform you participate in. By combining data collected within each domain as part of the platform, the researchers can investigate and compare treatment strategies and infection outcomes across a broader range of participants.

This is a domain within the RATIONAL Platform Trial to test the effectiveness and safety of stopping Ig replacement with or without prophylactic antibiotics compare to continuing Ig replacement.

Inclusion Criteria: 1. Patients must be receiving Ig (IV or subcutaneous - SCIg) replacement for prevention of bacterial infections due to hypogammaglobulinaemia for at least 6 consecutive months. 2. Patient is eligible for trial of Ig cessation in the opinion of the treating clinician and local investigator. 3. Patient is willing and able to comply with each of the treatment arms. Exclusion Criteria: 1. Prior or planned allogeneic haematopoietic stem cell transplantation. 2. Major infection (Grade 3 or higher) in preceding 3 months, and/or current active infection requiring systemic antimicrobial treatment. 3. Already receiving systemic antibiotic prophylaxis for the purpose of preventing bacterial infection (NB: patients may receive antiviral, antifungal and PJP prophylaxis). 4. Intolerance of all trial antibiotic options in either arm A or arm B. 5. Communication, compliance or logistical issues that are likely to limit patient's ability to take prophylactic or emergency antibiotics, or to obtain urgent medical attention for symptoms of infection. 6. Pregnant or breastfeeding. 7. Severe renal impairment (estimated or measured creatinine clearance of \< 30 mL/min). 8. Previous splenectomy. 9. Previous participation in this domain. 10. Treating team deems enrolment in the domain is not in the best interests of the patient.