Age-specific prevalence of antibodies to hepatitis A in Santiago, Chile: risk factors and shift in age of infection among children and young adults.

Abstract
Transition from high to lower endemicity of hepatitis A virus (HAV) infection may portend increased public health burden with the shift of infection to older ages and increasing morbidity and mortality. This report describes age-specific prevalence of antibodies to HAV (anti-HAV) among children and young adults in Santiago, Chile, compared with previous prevalence data and assesses factors predictive for anti-HAV. In 1998, a serosurvey was performed in Metropolitan Santiago, designed to enroll a representative, age-stratified population on the basis of area of residence. A total of 784 individuals (age range, 1-24 years) were enrolled. Anti-HAV prevalence by year of life was as follows: ages 1 to 4, 12.5%; 5 to 9, 26.2%; 10 to 14, 43.4%; 15 to 19, 57.4%; 20 to 24, 73.9%. Adjusting for age, factors associated (inversely) with anti-HAV included residential areas of higher socioeconomic status (SES), parental education, and household characteristics of potable water, municipal sewage system, and the presence of a toilet or refrigerator in the house. In logistic regression analysis, only maternal years of education and residence in areas of higher SES remained independently associated with anti-HAV. Excluding those from higher SES areas, comparison of the age-specific anti-HAV prevalence data from previous studies of similar methodology in areas of lower SES revealed consistent decreases across all age groups; the age-standardized prevalence for this age range (1-24 years) dropped from 53.7% in 1990 to 40.6% in 1998. In light of the growing pool of susceptible individuals at older ages, with HAV continuing to circulate in the communities, evaluation of the feasibility of vaccination programs would be judicious.

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