Hepatitis A antibodies: prevalence and persistence in a group of Mexican children.

The prevalence of antibodies against hepatitis A virus (anti-HAV) was evaluated in sera from 275 asymptomatic infants and children under the age of five years and in 46 maternal-cord serum pairs, followed by sera obtained thereafter each month from the first to the fifth month of life in 29, 17, 9, 9 and 7 infants (a total of 163 serum samples). Anti-HAV was found in all cord blood sera, but its prevalence declined progressively to 0% among 19 infants aged eight months. Four (25%) of 16 children aged one year had positive anti-HAV and the antibody prevalence was 89% in children five years old. Recent hepatitis A infection shown by circulating anti-HAV immunoglobulin M was detected in five infants under the age of two months and with frequencies ranging from 19-67% in one- and five-year-old children. It was concluded that in children living in Mexico City, hepatitis A infections occur at an earlier age and at higher rates than in children in other cities, especially those in developed countries.