Chronic hepatitis B (CHB) is a serious liver disease worldwide, and the leading cause of cirrhosis and hepatocellular carcinoma (HCC).HBsAg loss/seroconversion is considered to be the ideal endpoint of antiviral therapy in both HBeAg-positive and HBeAg-negative patients, as well as the ultimate treatment goal in CHB. However, some patients who have achieved HBsAg loss would reverse back to HBsAg positive, or even become HBV reactive with recurrence of viremia. In current study, the viral and HBsAg response in patients who have achieved HBsAg loss by interferon (IFN) treatment will be observed for 96 weeks after the completion of IFN treatment. The primary analysis will be performed at the end of 96 weeks. Following the completion of the study period of 96 weeks, patients will be offered to participate in a long term study for further observation of additional 144 weeks (total of 240 weeks from the enrollment).

Chronic hepatitis B patients who have achieved HBsAg loss from interferon treatment will be enrolled and observed for 96 weeks. Serum HBV DNA, HBsAg, anti-HBs, HBeAg, and anti-HBe will be measured every 3 months during the observation period. Their liver function and chemistry tests are also performed every 3 months. The liver ultrasonic examination would be taken every 3-6 months. The primary measurement is the percentage of patients who have positive HBsAg and/or a detectable level of HBV DNA. Following the completion of the study period, patients will be offered to participate in a long term study for further observation of additional 144 weeks.

Inclusion Criteria:

• Patients who had chronic hepatitis B and achieved HBsAg loss by interferon treatment.

Exclusion Criteria:

• Active consumption of alcohol and/or drugs
• Co-infection with human immunodeficiency virus, hepatitis C virus, or hepatitis D virus
• History of autoimmune hepatitis
• Psychiatric disease
• Evidence of neoplastic diseases of the liver

The study population in this study is composed of patients who have chronic hepatitis B and achieved HBsAg loss from interferon treatment. Eligible patients will have serum HBsAg and HBV DNA tests every 3 months for 96 weeks after finishing the interferon treatment. The sustained HBsAg response is defined as the levels of serum HBsAg mantaining below the low level of quantitation and the levels of HBV DNA remain undetectable. Following the completion of the study period, patients will be offered to participate in a long term study for further observation up to 240 weeks.