Rubella seroepidemiology among Korean women: Two decades after a combined vaccination strategy

Objectives: The aim was to examine 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. Methods: The serum IgG data of 72 114 women aged 20-49 years, who had undergone rubella antibody testing at the Gangnam CHA Medical Center between 2004 and 2018, were examined. A serum IgG level <10.0 IU/ml was considered negative. The study population was divided into three cohorts based on the vaccination policy: cohort 1, 1955-1976 (no national immunization program); cohort 2, 1977-1985 (national rubella only vaccination for high schoolers); cohort 3, 1986-1993 (combination strategy). We compared the rate of seronegativity and the adjusted odds ratio (OR) of seronegativity of each cohort. Results: The overall proportion of seronegative women decreased significantly, from 6.1% in 2004 to 2.5% in 2018 (Kendall tau = 0.89, p < 0.001). The rate of seronegativity was 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 year of testing, the OR for seronegativity was lower for cohort 2 (adjusted OR 0.68, 95% confidence interval (CI) 0.60-0.76) and cohort 3 (OR 0.55, 95% CI 0.40-0.75) when compared to cohort 1. Conclusions: Women who were covered by either vaccination program were less susceptible to rubella infection, supporting the value of both approaches. The study findings will serve as empirical evidence for an immunization program targeted towards young women and children. (C) 2020 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.