Age-specific prevalence of hepatitis A virus antibody in Thailand.

Serum specimens drawn at random from three geographically defined populations of healthy Thais were tested for antibody to the hepatitis A virus (anti-HAV) by radioimmunoassay. A total of 746 specimens were tested. The age by which 50 per cent were antibody positive was 4-5 years for residents of an urban Bangkok housing project, 8-9 years for rural villagers, and 10-11 years for urban Bangkok government school pupils. Overall, specimens from 97 per cent of Thai adults 16 years of age or older were anti-HAV positive. These data suggest widespread distribution of HAV in Thailand.