Rubella immunity levels in the United States population: Has the threshold of viral elimination been reached?

After the 1989-1991 rubella resurgence, rubella vaccination efforts targeted children and women of childbearing age. Utilizing National Health and Nutrition Examination Survey data collected during 1988-1994 and 1999 2004, we assessed whether US levels of rubella seropositivity are consistent with rubella elimination and whether changes are consistent with immunization efforts. Serum samples with rubella antibody levels >= 10 IU tested by rubella immunoglobulin G enzyme immunoassay were considered to be positive. In 1999-2004, the overall age-adjusted rubella seropositivity level was 91.3% (95% confidence interval [CI], 90.5%-92.1%), a significant increase from 88.1% (95% CI, 86.9%-89.1%) in 1988-1994 (P <.001). Among children, seropositivity was highest in children 6-11 years of age (96.2%), followed by adolescents 12-19 years of age (93.7%). Both groups showed significant increases in immunity levels, in comparison with those in 1988-1994 (P <.001). Among adults, seropositivity among women increased (from 88.9% to 91.5%; P=.015), and there was no change among men (from 87.8% to 88.0%;). In 1999-2004, population rubella immunity levels were at or above the modeled threshold for elimination of rubella virus transmission. Increases in immunity levels are consistent with vaccination efforts.