Efficacy of Peginterferon Alfa-2b in Previously Untreated Subjects With Chronic Hepatitis B and D Co-infection (Study P04603)

Inclusion Criteria: * Participants must demonstrate their willingness to participate in the study and comply with its procedures by signing a written informed consent. * Age 18-65 years old. * HBsAg positive \>6 months. * ALT \>= 2 ULN \>6 months. * HDV RNA positive serology. * Serum antibody to hepatitis delta antigen of IgG and IgM class. * Knodell score HAI \>= 6 and F \>= 0; positive test for intrahepatic Delta antigen in liver biopsy. * Women of childbearing potential (includes women who are less than 1 year postmenopausal and women who become sexually active) must be using an acceptable method of birth control (e.g., hormonal contraceptive, medically prescribed IUD, condom in combination with spermicide) or be surgically sterilized (e.g., hysterectomy or tubal ligation). * Participants must be free of any clinically significant disease (other than chronic hepatitis B and D), that would interfere with study evaluations. * Participants must understand and be able to adhere to the dosing and visit schedules, and agree to record symptom severity scores, medication times, concomitant medications, and adverse events accurately and consistently in a daily diary. Exclusion Criteria: * Age \<18 and \>65. * Concomitant HCV and/or HIV infection. * Actual liver failure (total serum bilirubin \>2.5 x normal, prolonged prothrombin time \>3 sec, serum albumin \<3 g/dl, history of ascites, variceal bleeding, or hepatic encephalopathy). * Toxic or autoimmune hepatitis (ANA titers \> 1:160), metabolic liver diseases (Wilson disease, hemochromatosis, α-1 antitrypsin deficiency) * Women who are pregnant or nursing. * Leukopenia (\<2500/mm\^3), neutropenia (\<1000/mm\^3), hemoglobin \<10 g/dl, presence of other severe diseases (myocardiopathy, diabetes mellitus, arterial hypertension, neoplasia, neurologic diseases, malnutrition). * Antiviral, immunomodulatory, corticosteroid, or chemotherapeutical treatment within 6 months of the participation in the study. * Depression and/or psychiatric disorders.