Additional Study Information: This study will be performed to determine if Panzyga (the study drug) can help with preventing infections in patients who have chronic lymphocytic leukemia (CLL). Panzyga is a study drug administered via injection into the vein, which contains human antibodies also called immunoglobulins. It is manufactured by Octapharma. Your participation in this clinical study will last for about 55 weeks. The study will be conducted at approximately 50 study centers worldwide. In total, at least 256 adult patients will take part in this study.