TAK-771 includes Immune Globulin Infusion (IGI) 10% and Recombinant Human Hyaluronidase (rHuPH20). Participants will receive SC infusion of rHuPH20 solution at a dose of 80 U/g IgG first, followed by SC infusion of 10% IGI within 10 minutes of completion of the infusion of rHuPH20 solution.

Immune Globulin Infusion (IGI) 10% and Recombinant Human Hyaluronidase (rHuPH20)

An Adverse event (AE) was any untoward medical occurrence in a clinical investigation participant administered a pharmaceutical product that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including a clinically significant laboratory finding), symptom, or disease temporally associated with the use of a investigational product, whether or not causality is suspected. A TEAE was defined as any event emerging or manifesting at or after the initiation of treatment with an investigational product or medicinal product or any existing event that worsened in either intensity or frequency following exposure to the investigational product.

Participants who developed anti-rHuPH20 binding antibody titers of >=1:160 and neutralizing antibodies to rHuPH20 was reported.

Participants continued TAK-771 (IGI 10% + rHuPH20) administration at the same dose and frequency they had in the Study TAK-771-3004 (NCT05150340) with dosing intervals of either 3 or 4 weeks, until the commercial TAK-771 becomes available at each study site or study termination. Participants received SC infusion of rHuPH20 solution first at a dose of 80 U/g, followed by SC infusion of 10% IGI within 10 minutes of completion of the infusion of rHuPH20 solution. The dose of TAK-771 was adjusted to maintain the target IgG trough level of >=5 g/L.

An Adverse event (AE) was any untoward medical occurrence in a clinical investigation participant administered a pharmaceutical product that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including a clinically significant laboratory finding), symptom, or disease temporally associated with the use of a investigational product, whether or not causality is suspected. A TEAE was defined as any event emerging or manifesting at or after the initiation of treatment with an investigational product or medicinal product or any existing event that worsened in either intensity or frequency following exposure to the investigational product.

EXSAS included all enrolled participants who received investigational drug in Study TAK-771-3005 at least once.

Participants continued TAK-771 (IGI 10% + rHuPH20) administration at the same dose and frequency they had in the Study TAK-771-3004 (NCT05150340) with dosing intervals of either 3 or 4 weeks, until the commercial TAK-771 becomes available at each study site or study termination. Participants received SC infusion of rHuPH20 solution first at a dose of 80 U/g, followed by SC infusion of 10% IGI within 10 minutes of completion of the infusion of rHuPH20 solution. The dose of TAK-771 was adjusted to maintain the target IgG trough level of >=5 g/L.