(HealthDay News) — Prenatal screening followed by immunoprophylaxis for infants of mothers with chronic hepatitis B virus (HBV) infection decreases perinatal transmission, according to research published online May 27 in the Annals of Internal Medicine.

Ai Kubo, PhD, of Kaiser Permanente in Oakland, CA, and colleagues conducted an observational study of 4,446 infants born to 3,253 HBV-positive mothers. The authors sought to assess the efficacy of an immunoprophylaxis program.

The researchers found that the infant HBV infection rates per 100 births were 3.37 (95% confidence interval [CI], 2.08–5.14) for e antigen-positive mothers and 0.04 (95% CI, 0.001–0.24) for e antigen-negative mothers. Among mothers who received testing, the lowest viral load level associated with transmission of HBV was 6.32 × 10IU/mL. Infection rates per 100 births were 3.61 (95% CI, 0.75 to 10.56) among mothers with viral loads of ≥5 × 107IU/mL (83 births) and 0 among mothers with viral loads <5 × 107IU/mL (831 births), regardless of e antigen status.

“A negative e antigen status or a viral load <5 × 107IU/mL (90.9% of women tested) identifies women at extremely low risk for transmission after immunoprophylaxis who are unlikely to benefit from further interventions,” the authors write.

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