Transmission profile of hepatitis B virus infection in the Batam region, Indonesia. Evidence for a predominantly horizontal transmission profile.

The aim of this study was to describe the distribution of hepatitis B virus markers among the autochthonous and immigrant multicultural populations of Riau province, Indonesia, in order to define the groups at risk and their infrastructure. This investigation was part of a large hepatitis B vaccination study. A total of 9701 healthy individuals, aged 5 years or older and living in the urbanised area of Batam, near Singapore, and on the surrounding islands were included. Socio-epidemiological data were collected, blood was drawn, and sera were tested for antibodies to hepatitis B core (anti-HBc) and surface antigen (anti-HBs). Anti-HBc-positive sera were tested against hepatitis B surface antigen (HBsAg). All tests comprised immunoassays from Roche (Germany) using Elecsys 2010. Complete data were available from 9314 subjects. The results showed relatively low prevalences of anti-HBc (a marker of a previous hepatitis B infection) and HBsAg in the 5-year-old chiLdren (5.8 and 1.9%, respectively) that increased continuously with increasing age. High anti-HBs levels (>1000 IU/L) were found in all age cohorts, indicating a lifelong threat of active hepatitis B infection. In conclusion, the transmission profile of hepatitis B appeared to be mainly horizontal (person-to-person) in the highly endemic region studied. Vertical transmission was less than 5%. The horizontal transmission routes included non-sexual activities of life since children <10 years of age also showed considerable infection rates. The results underline the need for catch-up hepatitis B vaccination programs for children and adults.