GamaSTAN S/D (Grifols Therapeutics, Inc., Research Triangle Park, North Carolina) is a sterile, preservative-free solution of immune globulin (IG) for intramuscular administration and is used for prophylaxis against disease caused by infection with hepatitis A, measles, varicella, and rubella viruses (1). GamaSTAN S/D is the only IG product approved by the Food and Drug Administration for hepatitis A virus (HAV) prophylaxis. In July 2017, GamaSTAN S/D prescribing information was updated with changes to the dosing instructions for hepatitis A preexposure and postexposure prophylaxis indications. These changes were made because of concerns about decreased HAV immunoglobulin G antibody (anti-HAV IgG) potency, likely resulting from decreasing prevalence of previous HAV infection among plasma donors, leading to declining anti-HAV antibody levels in donor plasma (2). No changes in dosing instructions were made for measles, varicella, or rubella preexposure or postexposure prophylaxis.