Efficacy, Safety, and Pharmacokinetics of Shu Yang IVIG

This is a Phase III, open-label, prospective, single-arm, multicenter trial to evaluate the efficacy of IVIG in maintaining the average of severe bacterial infections in less than one per year. The safety and pharmacokinetics (PK) of the investigational product will also be evaluated. Fifty male or female patients aged up to 60 years old will be selected. At least 20 patients must be up to 17 years old. During the trial, at least 20 adult patients will be invited to make up the PK assessment subgroups. After obtaining the signed Informed Consent/Assent Form , the screening procedures will be performed including the immune deficiency history from the medical records and safety exams. Patients will start the trial with a run-in period to stabilize the IgG trough levels. This period could last two to six visits with posological adjustments until the last two IgG trough levels are above 4 (5) g/L. After the run-in, the one-year test period will start at the V0. Depending on the treatment regimen, the patients will receive IVIG every 21 days (±3 days) up to day 378 or every 28 days (±4 days) up to day 364 when the close-out visit will occur. In all visits from all patients, a blood sample will be collected immediately before each IVIG administration to assess the IgG trough levels. To assess the investigational product PK properties, a group of 20 patients will collect additional blood samples for dosing IgG levels between Visit 4 and Visit 5. Those taking IVIG every 21 days, will collect six additional blood samples at the following times after the injection 30 min, 2h, 24h, 72h, 7 days, and 14 days. Those taking IVIG every 28 days will collect seven additional blood samples at the times 30 min, 2h, 24h, 72h, 7 days, 14 days, and 21 days. Adverse events will be collected at all visits to fulfill the safety endpoints. Moreover, the patients will have continuous access to the investigator's team to report adverse events, be instructed about how to proceed, or even perform Extra visits for presential medical evaluation. Additionally, the patient will receive a diary to record AEs, any medication taken, infections of any kind, days of hospitalization, and days missed from major activities due to infections. Trial duration: Each patient can participate in the trial for a maximum period of approximately 540 days from the time of signing the ICF or IAF until the close-out visit, including a Run-in period, depending on treatment regimen. Blinding and Randomization: This is an open-label trial; no blinding and randomization procedures will be applied.