Shifting susceptibility to hepatitis A among children and adolescents over the past decade.

OBJECTIVES To estimate the prevalence of anti-hepatitis A virus (anti-HAV) antibodies in serum samples from children and adolescents obtained at two clinical pathology laboratories in the city of Porto Alegre, south of Brazil, and to compare findings to those of a study carried out in the 1990s. METHODS In this cross-sectional study conducted between 2007 and 2008, 465 serum samples obtained from subjects aged 1-19 years were consecutively tested to determine the prevalence of total anti-HAV antibodies. Samples were provided by a public laboratory (group 1) that serves the Unified Health System exclusively, meant to represent the lowest socioeconomic strata, and by a private laboratory (group 2), meant to represent the higher socioeconomic classes. Tests were performed at a single laboratory using commercially available electrochemiluminescence kits. Antibody levels ≥ 20 UI/L were considered positive. RESULTS The seroprevalence of anti-HAV in Group 1 was 37.6%. The percentage of anti-HAV reactivity increased from 19.4% in the 1-to-4 group to 54.1% in the 15-to-19 group. In Group 2, overall anti-HAV positivity was 46.1% and was inversely correlated with age, declining from roughly 50% in the youngest groups to 29.1% in the 15-to-19 group. Comparison of sample findings to those reported in a 1990s study showed a significant reduction in anti-HAV prevalence among 5-to-9-year-olds in group 1 (p = 0.03). CONCLUSIONS The results suggest that the endemicity of hepatitis A in Porto Alegre has been declining over the past decade, and that children and adolescents, particularly those in the lowest socioeconomic strata, are more susceptible to the disease.