OBJECTIVETo conduct a prospective randomized controlled trial of infants born to hepatitis B virus (HBV) surface antigen (HBsAg)-positive mothers in order to investigate the dynamic changes in the titer of anti-HBV surface protein (HBS) induced by treatment with combined immunoprophylaxis (200 IU hepatitis B immunoglobulin (HBIG) and 5 or 10 mug yeast recombinant hepatitis B vaccine), to compare the protective effect of 5 and 10 mug hepatitis B vaccine, and to provide an immunization strategy, monitoring mode and booster immunization schedule for the high-risk group.

METHODSTwo-hundred-and-sixty-nine infants born to HBsAg positive mothers were given combined immunoprophylaxis at birth, and the venous blood samples (at birth, and 1, 7 and 12 months) were tested for HBV DNA load, and HBsAg and anti-HBS titers.

RESULTSThe overall 1-year protective rate of combined immunoprophylaxis was 95.9%. There was no significant difference between the infectious rates of infants given the 5 mug or the 10 mug hepatitis B vaccine (x2 = 0.876, P = 0.377). The geometric mean titers (GMTs) of anti-HBS were 144.1 mIU/ml at 1-month old and 564.9 mIU/ml at the age of 7 months old (the highest point), but declined to 397.6 mIU/ml at the age of 12 months old. The rate of infants with anti-HBS titer less than 100 mIU/ml was 20.9%, and that of less than 10 mIU/ml was 7.4% at 7-month-old; the rate of infants with anti-HBS titer less than 100 mIU/ml increased to 30.2% and that of less than 10 mIU/ml increased to 15.9% at 12-month-old. At 7-month-old, the GMT of the 10 mug vaccine group was higher than that of the 5 mug vaccine group (675.3 mIU/ml vs. 25.0 mIU/ml, P = 0.001) and the rate of infants with anti-HBS titer less than 10 mIU/ml was significantly lower in the 10 mug vaccine group (2.3% vs. 12.6%, P = 0.002); at 12-month-old, the rate of infants with anti-HBS titer less than 100 mIU/ml was also significantly lower in the 10 mug group (20.6% vs. 40.2%, P = 0.001).

CONCLUSIONCombined immunoprophylaxis is therapeutically efficacious for treating infants born to HBsAg positive mothers. Monitoring these infants' anti-HBs titer will help to identify non- or low-responders in a timely manner. The high-dose hepatitis B vaccine is preferable to the low-dose, and should be considered for use in immunization strategies for these infants.