The goal of this observational study is to prospectively follow chronic hepatitis B patients who had HBsAg decline in the past 12 months prior to screening. The main question it aims to answer are:

- Describe treatment pattern and its impact on HBsAg loss in hepatitis B patients who had HBsAg decline in past 12 months due to any reason (with or without new molecular entities therapy).

Participants will be followed up for 36 months after enrollment and may be extended upon expiration according to study objectives.

This study is a retrospective and prospective follow-up study for participants who had HBsAg decline in past 6 months due to any reason (with or without new molecular entities therapy). The follow-up period will be 3 years (36 months after enrollment) and may be extended upon expiration according to study objectives. Patients are treated or untreated based on current clinical practice guidelines, and every medical decision and course of treatment will reflect exclusively the decision of the treating physician in a routine clinical situation. The conduct of this non-interventional follow-up study and its documentation procedures will not affect the routine treatment of the subjects. It is only requested that any medical decisions, procedures and data during this study be documented in the electronic case report/record form (eCRF) according to the study protocol as available from routine medical care. Diagnostic testing and monitoring procedures are exclusively based on the decision of the treating physician.

In general, patients with hepatitis B should be monitored at least twice a year (every 6 months), every 12 weeks during NUC therapy and every 2 to 4 weeks during interferon-α therapy in accordance with clinical needs (Table 3-1 and Table 3-2). For patients had HBsAg decline in past 6 months due to new molecular entities therapy, The baseline of this follow-up study is the time when NME discontinued (within 28 days of the last does of NME or within 2 half-life period of the NME). For patients had HBsAg decline in past 6 months without new molecular entities therapy, the baseline should be the time of enrolling in the study. The time of enrolling in this study may be posterior or equal to baseline, which is not necessarily the baseline of this study. The visit window period is ±28 days for patients with NUC therapy and ±7 days for patients with interferon-α therapy. Follow-up study visit data can be collected retrospectively if it has been performed before entry of this study.

Medical decisions, procedures and data before this follow-up study will also be documented if available. Participants will be asked to store a certain amount of blood samples in site during study visit for future HBV markers, host immunity or other related tests. The retained remaining samples from previous tests before this follow-up study may also be used for HBV related exploratory research after patient informed consent.

Inclusion Criteria:

• Participants must have HBsAg decline ≥0.5 log10 IU/mL in past 12 months prior to screening due to any reason (with or without new molecular entities therapy). Among the enrolled subjects, 70% must have HBsAg decline ≥1 log10 IU/mL or actual values ≤3 log10 IU/mL.
• Able and willing to provide written informed consent and to comply with the study protocol according to International Council for Harmonization (ICH) and local regulations.

Exclusion Criteria:

• Any condition which, in the opinion of the investigator, contraindicates their participant in this study.
• Participants who are currently participating in interventional clinical study exploring HBV treatment.

Participants must have HBsAg decline ≥0.5 log10 IU/mL in past 12 months prior to screening due to any reason (with or without new molecular entities therapy). Among the enrolled subjects, 70% must have HBsAg decline ≥1 log10 IU/mL or actual values ≤3 log10 IU/mL.