We examined rubella seronegativity among women of childbearing age after the introduction of rubella-containing vaccine (RCV) among teenage girls and universal MMR programs in South Korea.
We examined the data of serum IgG data of 72,114 women aged 20-49 years at the Gangnam CHA Medical Center from 2004 to 2018. Values with serum IgG level <10.0 IU/ml were considered negative. Based on the vaccination policy, the study population was divided into three cohorts-Cohort 1, 1955-1976 (no national immunization program), Cohort 2, 1977-1985 (national rubella only vaccination for high schoolers), and Cohort 3, 1986-1993 (combination strategy). We compared the rate of seronegativity, and adjusted odds ratio (OR) of seronegativity of each cohort.
Overall proportion of women with seronegativity had also decreased significantly, from 6.1% in 2004 to 2.5% in 2018 (Kendall’s tau = -0.89, P<0.001). The rate of seronegativity was the highest among women who were not targeted for national immunization (born in 1955-1977, 5.2%), while it was lowest among candidates receiving routine and catch-up vaccinations (born in 1986-1993, 2.2%). When controlling for the effect of age and the year of test, the ORs for seronegativity for Cohort 2 (adjusted OR: 0.68, 95% confidence intervals [CI]: 0.60, 0.76) and Cohort 3 (OR: 0.55, 95% CI: 0.40, 0.75) were lower than those of Cohort 1.
Women who were covered by either vaccination program were less susceptible to rubella infection, supporting the value of both approaches. This finding will serve as an empirical evidence for immunization program targeted toward young women and children.

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