The purpose of the study is to assess the impact of immunoglobulin treatment by subcutaneous injections every 2 weeks (biweekly) on a cohort of patients with primary and secondary immune deficiencies. The full study will consist of safety, efficacy and Quality of Life (QoL) evaluations and a pharmacokinetic (PK) sub-study. The primary objectives of the study are to determine tolerability and safety of biweekly IgPro20 injection regimen and to compare PK outcomes on weekly and biweekly IgPro20 therapy.