Measles antibody trough levels after treatment with immunoglobulin products and predicted levels assuming lower measles antibody specifications.

BACKGROUND Widespread vaccination against measles has resulted in decreasing measles antibody levels in human immune globulin (IG) products. As levels continue to decline, it needs to be determined whether the release specifications for measles antibody levels in IG products can be lowered and still provide protection against infection for patients who receive IG treatment for primary immunodeficiency disease. STUDY DESIGN AND METHODS Trough level measles neutralizing antibodies were measured in 10 pediatric patients with primary immunodeficiency disease (ages 2-16) treated with IG administered both by intravenous and subcutaneous infusion. The results were used to model worst-case (lowest) serum measles antibody levels in two cases: 1) the current case with intravenous dosage at 300 mg/kg at a measles antibody level of 0.48x Center for Biologics Evaluation and Research Reference 176 and 2) a future case with intravenous dosage at 400 mg/kg and 0.30x Center for Biologics Evaluation and Research Reference 176. RESULTS Serum trough measles neutralizing antibody levels were an average of 11-fold or greater above minimum protective levels for immunocompetent individuals of 0.12 IU/mL in both the intravenous and subcutaneous phases of the study. Modeling using both the current worst-case dose and future case shows average levels for IG intravenous/subcutaneous infusion of 3.9/4.8- and 3.2/4.0-fold above 0.12 IU/mL for the two cases, respectively. CONCLUSION Lowering the measles antibody level specification to 0.30x Center for Biologics Evaluation and Research Reference 176 in IG products will still provide trough serum antibody levels against measles infection of greater than 0.12 IU/mL when dosed at 400 mg/kg or higher.