[Indices of collective immunity to the hepatitis A virus in different geographical regions].

Antibodies to hepatitis A virus were determined in the sera of healthy population by enzyme immunoassay techniques. The distribution of antibodies in different age groups was compared, taking into account the proportion of persons with high, moderate and low titers. Among the surveyed regions, the highest proportion of nonimmune persons was detected in Moscow (45 %) and the lowest proportion, in Aralsk (7%) and Mongolia (3%). In some regions (Moscow, Vilnius) the characteristic feature of the immune structure of the population was the gradual increase of the occurrence of antibodies and their levels with age, while in other regions (Aralsk, Mongolia) the intensive acquisition of antibodies occurred at younger ages with a subsequent decline in antibody levels. Some of the possible mechanisms of the formation of population immunity to hepatitis A are discussed.