An Observational Study in Participants With Chronic Hepatitis B (CHB) Receiving Therapy With Peginterferon Alfa-2a 40 Kilodaltons (kD) (PEGASYS) - The PRO B Study

Inclusion Criteria: * HBeAg positive or HBeAg negative serologically proven CHB with or without cirrhosis (histologically verified at some point in the past) * Baseline HBV DNA greater than (\>) 2000 IU/mL * Elevated serum ALT \> upper limit of normal (ULN) * Participants treated with previous NAs therapy are eligible for this study Exclusion Criteria: * Participants who have contraindications for peginterferon alfa-2a in accordance with the approved summary of product characteristics (for example, severe psychiatric diseases, immunological diseases, severe hepatic dysfunction or decompensated cirrhosis of the liver severe retinopathy or thyroid dysfunction, autoimmune hepatitis, history of severe pre-existing cardiac disease, or hypersensitivity to the active substance, to alpha interferons, or to any of the excipients) * Participants with ALT \> 10 times of ULN or evidence of hepatocellular carcinoma * Participants with serological evidence of co-infection with hepatitis A virus, hepatitis C virus, human immunodeficiency virus, or hepatitis D virus * Participants with decompensated liver disease * Pregnant or breast-feeding women * A history of liver transplantation or planned for liver transplantation