Prevention of Vertical Transmission of Hepatitis B An Observational Study

Background: For mothers with chronic hepatitis B virus (HBV) infection, the Centers for Disease Control and Prevention recommends immunoprophylaxis to decrease perinatal transmission. However, its effectiveness and risk factors for failure have not been well-studied in community practice. Objective: To investigate the effectiveness of a contemporary immunoprophylaxis protocol. Design: Observational study. Setting: An HBV perinatal immunoprophylaxis program within Kaiser Permanente Northern California. Patients: 4446 infants born to 3253 HBV-positive mothers between 1997 and 2010. Measurements: Adherence to immunoprophylaxis, follow-up testing rates, maternal risk factors for HBV transmission, and transmission rates. Results: The infant infection rate was 0.75 per 100 births from 1997 to 2010 (Poisson 95% CI, 0.48 to 1.10). Rates per 100 births were 3.37 (CI, 2.08 to 5.14) for e antigen-positive mothers and 0.04 (CI, 0.001 to 0.24) for e antigen-negative mothers. Among mothers with viral load testing, the lowest level associated with transmission was 6.32 x 10(7) IU/mL. Infection rates per 100 births were 3.61 (CI, 0.75 to 10.56) among the 83 births to mothers with viral loads of 5 x 10(7) IU/mL or greater and 0 among the 831 births to mothers with viral loads less than 5 x 10(7) IU/mL, regardless of e antigen status. Limitations: Testing for HBV immunity and infection was less complete in earlier years. Viral load testing was only consistently available starting in 2007. Conclusion: Prenatal HBV screening followed by postnatal prophylaxis is highly effective in preventing vertical transmission of HBV. A negative e antigen status or a viral load less than 5 x 10(7) IU/mL (90.9% of women tested) identifies women at extremely low risk for transmission after immunoprophylaxis who are unlikely to benefit from further interventions.