The purpose of this study is to determine the optimal treatment duration of antiviral therapy for chronic hepatitis B.

Thymosin alpha1/interferon combination therapy has been known as an effective antiviral therapy for chronic hepatitis B. It is superior to interferon single therapy since the sustained viral response rate of combination therapy used to be about 70% compared with that of single interferon therapy(20%). Until now, the combination therapy including 6-month treatment of thymosin alpha1 has been as effective as 12-month treatment of thymosin alpha1. We hypothesized that thymosin alpha1 is an immune potentiator so, the shorter duration of thymosin alpha1 treatment might be as effective as the prolonged treatment duration. In detail, we designed to perform this clinical study comparing the combination of pegylated interferon and thymosin alpha1 with pegylated interferon alone. Total treatment duration of both parallel groups will be 12 months, and the combination therapy will be lasted for the first 3 months followed by the next, ongoing pegylated interferon single therapy for 9 months.