Seroprevalencia de la infección de Chagas y sus determinantes en población pediátrica de la región de Cochabamba, Bolívia / Seroprevalence of Chagas disease and its determinants in children and adolescents from Cochabamba, Bolivia

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Seroprevalence of hepatitis B in two period birth cohorts of Bolivian children: effect of universal vaccination.

BACKGROUND: Since 2000 universal routine immunization against the hepatitis B virus (HBV) was implemented in Bolivia. This study aimed to assess the seroprevalence of markers against HBV in two different birth cohorts (pre-universal vaccine cohort and post-universal vaccine cohort) from Cochabamba, Bolivia. METHODS: We performed a school-based seroepidemiological survey (n = 424) of HBV in 2010 in the Cochabamba region. An ELISA test was used to measure antibodies to the hepatitis B surface antigen (anti-HBs IgG) and to the hepatitis B core antigen (anti-HBc IgG). RESULTS: The prevalence of anti-HBs IgG in the pre-universal vaccine cohort was 5.8% (95% CI: 3.3-8.3%); it was higher in boys (9.1%), and those living in suburbs (9.7%). The anti-HBs IgG prevalence among post-universal vaccine cohort was 37.9% (95% CI: 28.5-48.1%), and was higher in children who spoke Quechua at home (51.0%), those living in suburbs (53.9%), and those born in 2005 (72.7%). Neither cohort showed differences relating to parental education. The prevalence of anti-HBc IgG was 1.1% among post-universal vaccine cohort and 1.2% among pre-universal vaccine cohort (p > 0.05). CONCLUSIONS: This study identified a persistent low seroprevalence of hepatitis B infection in spite of a decade of universal immunization, and low long-term humoral immunity against HBV infection in vaccinated children in Cochabamba. 

Seroprevalence of varicella-zoster virus infection in children from Cochabamba: tropical or temperate pattern?

OBJECTIVES: To determine the seroprevalence of varicella-zoster viral (VZV) infections in schoolchildren from the Cochabamba region (Bolivia), and its association with socio-demographic variables, socio-economic status and geographical location. METHODS: Seroepidemiological survey (n = 436) on VZV of schoolchildren living in the Cochabamba region of Bolivia in 2010. An ELISA test was used to measure varicella antibodies. Parents or guardians completed a questionnaire regarding socio-demographic information (age, gender, living area, parental educational level, presence of siblings and number of family members in the household), and a blood sample was collected from each child to check for VZV antibodies. A descriptive and bivariate analysis was performed. RESULTS: The global prevalence of VZV was 78.2% (95% CI 74.3-82.1). It was higher in females (82.1%), pre-adolescents (aged 10.1-13 years: 81.4%) and adolescents (aged >13 years: 80.2%), in children with less well-educated parents (81.3% to 81.6%), in warmer municipalities (81.4% to 82.2%), in rural areas (80.0%), in children with siblings (80.1%), those who although the latter association was not statistically significant. CONCLUSIONS: The prevalence of VZV infection in childhood was relatively high for a tropical country, and much closer to that of temperate countries prior to the introduction of varicella vaccine into vaccination programmes.

Measles in Bolivia: A 'honeymoon period'.

BACKGROUND: Although measles is a highly infectious disease, the live measles vaccine provides protection for over 20 years, and immunity may be lifelong. This study assessed measles seroprevalence in schoolchildren in the Cochabamba region of Bolivia. METHODS: A seroepidemiological survey of measles immunity in 5-16-year-old schoolchildren (n=441) living in the Cochabamba region of Bolivia was performed in March and April of 2010. Representative regional samples of school children from 14 schools were obtained. A parent-administered questionnaire collected sociodemographic and socio-economic status, and serum samples were tested for measles antibodies using an enzyme-linked fluorescent antibody test. The measles prevalence and corresponding 95% confidence intervals (CI) were calculated. A descriptive and bivariate analysis was performed using the ANOVA or the Kruskal-Wallis test according to whether the data were distributed normally (Kolmogorov-Smirnov test p-value<0.05) plus the chi-square test or Fisher's exact test as needed. RESULTS: The global seroprevalence of measles was 69.61% (95% CI 65.32-73.90) and was higher in adolescents (84.16%, 95% CI 77.04-91.28) and Spanish speakers (74.74%, 95% CI 68.56-80.92). The seroprevalence did not differ according to socio-economic status, living area, or number of family members in the household. CONCLUSIONS: This study found a high prevalence of measles susceptibility in Bolivian children. Thus, herd immunity may not have been established, and some outbreak could occur. Authorities should redress this situation before endemic measles transmission occurs nationally and regionally, and there is an urgent need to conduct more seroprevalence studies in the region.