Vaccine
http://www.sciencedirect.com/science/journal/0264410X
Volume 30, Issue 23 pp. 3355-3488 (14 May 2012)

Regular Papers
Seroprevalence of measles among children affected by national measles elimination program in Korea, 2010
Original Research Article
Pages 3355-3359
Eun Seong Kim, Young June Choe, Heeyeon Cho, You-Jin Kim, Hee Sook Yoon, Jeong-Sun Yang, Kisoon Kim, Geun-Ryang Bae, Duk-hyoung Lee

Abstract
Background
Following the implementation of national measles elimination plan in Korea, the elimination was declared in 2006. In order to sustain the elimination, high population immunity should be continuously monitored. To evaluate the current age-related susceptibility within the Korean population, we conducted the seroprevalence in children and adolescents who were affected by the national measles elimination plan.

Methods
We used residual serum specimens to measure measles specific IgG and geometric mean titer (GMT) in birth cohorts 2007–2008 and 1997–2003. Among birth cohorts, 2007–2008 cohorts were grouped to evaluate the timeliness of first dose of MMR, 1994–2003 cohorts were grouped to evaluate the effect of keep-up MMR2 campaign, and 1992–1993 cohorts were grouped to evaluate the effect of catch-up campaign in 2001.

Results
Overall, measles seropositivity rate was 86%. The highest seroprevalence of measles IgG was in birth cohorts 2007–2008. Measles seropositivity declined continuously in age groups. The birth cohorts 1994–1996 showed significantly lower levels of seropositivity and GMT than did the other birth cohorts.

Conclusion
Despite efforts to eliminate measles for the past 10 years in Korea, our study revealed specific birth cohorts remaining at risk for transmission. The adolescents born during 1994–1996 had the lowest measles seropositivity levels, and might represent a ‘pocket’ that has potential at increased risk for measles transmission. Further discussion for follow-up immunization should be placed for consideration in the near future.