Treatment cessation in chronic hepatitis B is associated with high rates of disease relapse. However patients who achieve the seroclearance of hepatitis B surface antigen (HBsAg) (<0.05 IU/mL) show good off-treatment durability after treatment cessation. Through the quantification of HBsAg, the study aims to investigate how low should quantitative HBsAg be before once can achieve successful disease control after treatment cessation.