This is a phase III, placebo controlled, double blind, randomized clinical trial to assess the efficacy and safety of tenofovir disoproxil fumarate (TDF) given from 28 weeks' gestation until 2 months postpartum to pregnant women with Hepatitis B (HB) virus (HBV) chronic infection and positive for HB s and e antigen to prevent perinatal transmission of HBV to their infants. All infants will receive HBV passive (HB specific immunoglobulin) and active (vaccine) immunization.~Chronic hepatitis B (CHB) infection is complicated by cirrhosis and hepatocellular carcinoma (HCC), the 10th leading cause of death worldwide.~In 2011, about 7% of adults in Thailand were HBsAg carriers. Infant hepatitis B (HB) immunization and HB immune globulin (HBIg) administered at birth effectively prevent most mother-to-child transmission (MTCT) of HBV. However, about 12% of mothers with high load of HBV transmit the virus to their infants, despite active and passive immunization.~Studies have suggested that antiviral treatment at the end of pregnancy and during early postpartum can reduce the risk of transmission to the child. A potential limitation to this approach is the risk of hepatic disease exacerbation following discontinuation of antiviral treatment postpartum, and this risk has not been properly evaluated. No randomized clinical trials have adequately demonstrated the efficacy and safety of maternal antiviral treatment the prevention of mother to child transmission of HBV. This is the reason why this approach is not currently recommended by the Associations for the Study of Liver Diseases.~We hypothesize that a potent antiviral, tenofovir, can decrease HBV viral load in HBV infected pregnant women and therefore reduce the risk of perinatal transmission, before infants are definitely protected by passive-active immunization. We also hypothesize that only moderate exacerbations of liver disease will be observed after discontinuation of a short antiviral course (5 months). While the primary objective of the study is to assess the efficacy of tenofovir versus placebo for the prevention of perinatal transmission, an important secondary objective is the assessment of the risk of postpartum hepatic disease exacerbation.~Within 2 years, 328 women and their infants will be enrolled from public hospitals in Thailand and randomized to receive either tenofovir disoproxil fumarate or matching placebo from 28 weeks of pregnancy until 2 months postpartum. Mothers and infants will be followed until one year postpartum.~The primary endpoint will be the detection of HBsAg and HBV DNA in infants at six months of life. An interim analysis will be conducted when half of the outcomes are available.
Chronic hepatitis B (CHB) infection is complicated by cirrhosis and liver cancer. In Thailand, 7% of adults are chronically infected by Hepatitis B virus (HBV). The risk of perinatal transmission of HBV is about 12% when a mother has a high HBV load in her plasma, even if her infant receive specific immunoglobulin and vaccine.~The hypothesis of this study is that a potent antiviral, tenofovir, can decrease HBV load in HBV infected pregnant women and therefore reduce the risk of perinatal transmission/ Pregnant women participating in this study will receive tenofovir or placebo during the last trimester of pregnancy and two months postpartum. The risk of perinatal transmission will be compared between the two groups.~The results of the study will help define policy to manage HBV infected pregnant women to prevent perinatal transmission.