Population measles seroprevalence: Heterogeneity by birth-year cohort

This work sought to estimate population measles seroprevalence and heterogeneity in the antibody concentration distribution that could be explained by the birth-year cohort according to the opportunity viral and vaccine exposure, applied to data from Medellín, Colombia. Prevalence of IgG antibodies was analyzed for measles based on a population study with a random sample of 2098 individuals from 6 to 64 years of age. Finite mixture models were used to estimate global seroprevalence and that of three birth-year cohorts (I: born up to 1982; II: 1983–1994; III: born since 1995). Multiple linear regression permitted adjusting the concentration of antibodies by cohort, zone, and sex. Globally, seronegativity was 6.5 % (95%CI 4.9–8.6), seropositivity of 78.4 (95%CI 75.1–81.4), and equivocal of 15.1 % (95%CI 12.5–18.1). Two components were found with skewed normal distribution, which reclassified those equivocal as seropositive. Differences were observed by cohort in the geometric mean of antibodies (Cohort I: 1704.6; II: 562.2; III: 802.1 mIU/mL) and seronegativity (Cohort I: 4 %; II:13.3 %; III: 8.9 %). Antibody concentration increased by 1.26 mIU/mL in residents in the rural area, while diminishing in individuals from cohort II (by 3.02 mIU/mL) and cohort III (by 2.14 mIU/mL). The younger cohorts (II and III) had lower antibody concentration (higher seronegativity), indicating the need to monitor periodically seroprevalence and an eventual reestablishment of the transmission in these groups with higher risk of infection.