The purpose of this study is to demonstrate the effect of IgPro10 on the prevention of serious bacterial infections in patients with primary immunodeficiency.

As secondary endpoints the rate of overall infections, the tolerability and safety of IgPro10 are studied.

A part of the patients are participating in a pharmacokinetic substudy.

Key Inclusion Criteria:

• Patients with primary immunodeficiency
• Patients who have received stable IVIG therapy at 3- or 4-weekly intervals for at least 6 months

Key Exclusion Criteria:

• Newly diagnosed PID
• Allergic reactions to immunoglobulins or other blood products
• Administration of steroids (daily ≥ 0.15 mg prednisone equivalent/kg/day) or other immunosuppressive drugs
• Concomitant diseases such as hypoalbuminemia, protein-losing enteropathies, kidney diseases with proteinuria, malignancies of lymphoid cells (e.g. lymphocytic leukemia), and recent history of migraine
• History of cardiac insufficiency (NYHA III/IV), cardiomyopathy, congestive heart failure, severe hypertension