Chronic HBV Infection in Pregnant Women Taking TAF to Prevent Vertical Transmission

Mother-to-child transmission is the main route of transmission of Hepatitis B Virus (HBV) in China, and about 30% - 50% of chronic HBV carriers are infected by this. Although the current hepatitis B vaccine combined with hepatitis B immunoglobulin scheme has achieved excellent results, about 5% - 10% of infants born to chronic hepatitis B (CHB) mothers are still infected. A pregnant women's blood hepatitis B virus load ≥ 2 × 10\^5 IU/mL before delivery is the main risk factor for transmission prevention failure. Two recent random controlled trial (RCT) studies have shown that the use of Tenofovir Disoproxil Fumarate (TDF) in highly viremic HBsAg positive mothers may safely reduce the rate of MTCT in comparisons between groups of TDF treated and untreated patients. Tenofovir Alafenamide (TAF) is the successor to TDF, and both drugs have a similar mechanism of action to reduce HBV DNA levels and normalize serum alanine aminotransferase (ALT) in chronic hepatitis B patients (CHB). TAF however, has a better safety profile with less adverse effects to hip and spine bone mineral density and renal function. Currently, TAF has been approved by the State Food and Drug Administration and marketed in China in December 2018. On the drug label, it has been suggested that TAF may be considered during pregnancy if necessary. However, it has not been reported whether the application of TAF in pregnant women can achieve better effects and safety in prevention of mother-to-child transmission. This prospective, triple arm, multicenter study seeks to evaluate the efficacy and safety of TAF in the prevention of mother-to-child transmission as compared to a retrospective cohort of mothers who were treated with TDF.