FAMILIAL CLUSTERING OF HEPATITIS-B VIRUS-INFECTIONS AND PREVENTION OFPERINATAL TRANSMISSION BY IMMUNIZATION WITH A REDUCED NUMBER OF DOSESIN AN AREA OF INTERMEDIATE ENDEMICITY (TUNISIA)

Hepatitis B surface antigen (HBsAg) was detected in 3.3% of 7162 pregn ant Tunisian women tested and HBeAg in 9.6% of the HBsAg-positive moth ers. Family members of 46 of these HBsAg-positive mothers (33 husbands and 61 children aged 1-6 years) were investigated for the presence of HB V markers. HBsAg was detected in 21% of the children and 18% of th e husbands. Fifty children born to HBsAg-positive mothers received hep atitis B vaccine at birth, at the age of 2-3 months and at the age of 9 months. After immunization, anti-HBs were detected in 92% of them wi th an anti-HBs geometric mean titre of 415 mIU ml(-1). Compared with t he HBsAg carrier state in older siblings, the protective efficacy was estimated to be 60%. It was 100% for infants born to HBeAg-negative mo thers, but only 31% for those born to HBeAg-positive mothers. For a be tter efficacy, the schedule of the EPI needs to be modified to include an immunization session at I month of age.