RESUMO
The primary objective of this study was to estimate the efficacy of a recombinant hepatitis B vaccine (H-B-VAXII) in preventing chronic hepatitis B infection when given alone without concomitant hepatitis B immune globulin (HBIG) to healthy Thai infants born of HBeAg-positive carrier mothers. The infants received a 0.5 ml (5 micro g HBsAg) intramuscular injection of H-B-VAXII either at birth, 1, and 6 months of age (Schedule A) or at birth, 1, 2, and 12 months of age (Schedule B). Blood drawings for the determination of hepatitis B virus (HBV) serologic markers were scheduled 4, 9, and 13 months following the initial dose of vaccine. At 13 months, 5 (10%) of 50 infants vaccinated on Schedule A and 7 (14.9%) of 47 infants vaccinated on Schedule B had experienced chronic HBV infection. Based on an expected infection rate in unimmunized infants of either 70 or 90%, the overall efficacy for both schedules combined was estimated to be 82.3% (95% CI: 70.6, 90.6) or 86.2% (95% CI: 77.1, 92.7), respectively. Corresponding schedule-specific estimates were for Schedule A: 85.7% (95% CI: 68.8, 95.3) or 88.9% (95% CI: 75.8, 96.3) and for Schedule B: 78.7% (95% CI: 59.6, 91.1) or 83.4% (95% CI: 68.6, 93.1). These results suggest that in areas of high endemicity, where mothers may not always be screened for HBV infection, routine vaccination of infants at birth with a course of hepatitis B vaccine alone should be highly protective, even for very high-risk infants of HBeAg-positive mothers.
