A qualitative and quantitative comparison of two rubella virus-specific IgG antibody immunoassays

Monitoring circulating rubella IgG antibody concentration in children and in women of child-bearing age is an important step in maintaining high levels of rubella immunity and preventing congenital rubella syndrome. The objective of this study was to evaluate the Beckman Coulter Access Rubella IgG assay against the Dade Behring Enzygnost Anti-Rubella-Virus/IgG EIA assay in serum of children (n = 342) immunized with two doses of measles-mumps-rubella-II (MMR-II) vaccine. We found that the two assays had a high qualitative (96%), and quantitative correlation 0.93 (0.92, 0.95), based on a protective antibody concentration of > or =15 IU/mL. The mean rubella antibody concentration measured by both assays was >37 IU/mL; however, 10% of our study participants had low concentrations of circulating rubella-specific antibodies. These findings might indicate a need for additional monitoring of antibody levels as these children reach child-bearing age, or potentially a need for a third dose of vaccine to increase seroconversion.