HEPATITIS-B IN URBAN AUSTRALIAN SCHOOLCHILDREN - NO EVIDENCE OF HORIZONTAL TRANSMISSION BETWEEN HIGH-RISK AND LOW-RISK GROUPS

Objective: To document the prevalence of hepatitis B virus (HBV) infec tion in urban Australian primary schoolchildren, and to look for evide nce of horizontal transmission of HBV in schools between children at h igh risk of infection and those at low risk. We compared the prevalenc e of infection in a group of low-risk children attending control schoo ls (less than 5% of students from high-risk groups) with the prevalenc e in low-risk children attending test schools (more than 20% of studen ts from high-risk groups). Methods and results: Venous blood was colle cted and tested tor hepatitis B markers by radioimmunoassay; 2883 chil dren (1431 boys) of mean age 11.3 years (SD, 0.7) from 50 schools were tested. Evidence of past or current infection was present in 169 chil dren (5.9%). This number comprised three of the 1347 low-risk children (0.2%), 10 of the 602 medium-risk children (1.7%), 154 of the 731 hig h-risk children (21.1%) and two of the 203 other children (1%). Fifty- four of the 169 infected children were hepatitis B surface antigen (HB sAg) positive, 36 of the 54 were also positive for hepatitis B e antig en (HBeAg). There was no difference between children in the low-risk g roup in test and control schools for markers of hepatitis B virus infe ction. Conclusions: A low prevalence of HBV infection was found in low -risk school-children irrespective of the proportion of high-risk chil dren in their classes. Targeting vaccination to infants and children w ith known risk factors is the most important strategy in low endemicit y countries; vaccination of children without risk factors could be del ayed till early adolescence.