Cross-sectional surveys of measles antibodies in the Jiangsu Province of China from 2008 to 2010: the effect of high coverage with two doses of measles vaccine among children.

ABSTRACT

BACKGROUND: Changes in the epidemiological characteristics of measles since 2007 appeared in the Jiangsu province. Although the reported coverage with two doses of measles vaccine was greater than 95% in most regions of the province, measles incidence remained high across the whole province. Cross-sectional serological surveys of measles antibodies in the Jiangsu province of China were conducted from 2008 to 2010 to assess and track population immunity. METHODS: Measles-specific IgG levels were measured in serum samples using ELISA. GMTs and seroprevalence with 95% CIs were calculated by region, gender, and age. ANOVA and χ(2) tests were used to test for statistically significant differences between groups for GMT levels and seroprevalence, respectively. RESULTS: Seroprevalence showed a significantly increasing trend annually (CMH χ(2) = 40.32, p<0.0001). Although the seroprevalence among children aged 2-15 years was consistently over 95%, vaccine-induced measles antibodies may wane over time. Measles seropositivity in the Jiangsu province was 91.7% (95% CI 90.1-93.2%) in 2010. Among adults aged 15 to 29-year-olds, the seropositivity rate was 88.4% (95% CI 82.7-92.8%). CONCLUSIONS: Vaccination strategies may need to be adjusted depending on the individual age and regions, particularly individuals between the ages of 8 months-14 years old and 20-29 years old. Additional SIAs are likely required to eliminate measles in China.