Familial clustering of hepatitis B virus infections and prevention of perinatal transmission by immunization with a reduced number of doses in an area of intermediate endemicity (Tunisia).

Hepatitis B surface antigen (HBsAg) was detected in 3.3% of 7162 pregnant Tunisian women tested and HBeAg in 9.6% of the HBsAg-positive mothers. Family members of 46 of these HBsAg-positive mothers (33 husbands and 61 children aged 1-6 years) were investigated for the presence of HBV markers. HBsAg was detected in 21% of the children and 18% of the husbands. Fifty children born to HBsAg-positive mothers received hepatitis 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 with an anti-HBs geometric mean titre of 415 mIU ml-1. Compared with the HBsAg carrier state in older siblings, the protective efficacy was estimated to be 60%. It was 100% for infants born to HBeAg-negative mothers, but only 31% for those born to HBeAg-positive mothers. For a better efficacy, the schedule of the EPI needs to be modified to include an immunization session at 1 month of age.