1. How low must serum HBsAg be for successful off-treatment durability? Must the "magic figure" of 0.05 IU/mL be reached? Or could an HBsAg level in the >0.05 - 200 IU/mL range be sufficient? This could have implications in drug budgeting. According to data retrieved from the Clinical Data and Analysis Reporting System (CDARS), Hospital Authority, NA prescription headcount in 2014 reached 36,287 prescriptions, with an estimated total drug expenditure of 381 million Hong Kong dollars. A finite duration of therapy for certain patients could help in the reduction of drug expenditure.