RATIONALE: Hepatitis B antigen peptide (HBsAg) vaccine may help the body build an immune response and help prevent hepatitis B. PURPOSE: This clinical trial studies edible HBsAg vaccine therapy in healthy participants who have undergone previous vaccination.

OBJECTIVES: I. To evaluate the safety, tolerability, and immunogenicity of orally delivered HBsAg that is formulated as an expressed protein in transgenic potato tubers (HBV-EPV) at different doses and schedules. OUTLINE: Patients are randomized to 1 of 4 treatment arms. ARM I: Participants consume placebo HBV-EPV on days 0, 14, 28, and 56. ARM II: Participants consume HBV-EPV expressing HBsAg on days 0 and 28 and placebo HBV-EPV on days 14 and 56. ARM III: Participants consume HBV-EPV expressing HBsAg on days 0, 28, and 56 and placebo HBV-EPV on day 14. ARM IV: Participants consume HBV-EPV expressing HBsAg on days 0, 14, 28, and 56. After completion of study treatment, patients are followed up at days 70, 84, 98, and 114.

Inclusion Criteria:

• All Roswell Park Cancer Institute (RPCI) staff, faculty, and students, who are in good health
• Participants confirmation of history of primary immunization series with recombinant hepatitis B (HB) vaccine (last dose at least one year prior to screening anti-HBs level assessment)
• Current anti-HBs levels less than or equal to 115 mIU/mL
• Major organ functions within acceptable medical limits as determined in routine clinical laboratory screening tests
• Expected availability for the duration of the study period
• If female, then documentation that the subject is not pregnant by an acceptable laboratory test and that the subject is using an adequate birth control method to prevent pregnancy for at least 3 months following the last immunization in the study
• Human immunodeficiency virus (HIV) antibody negative
• Ability to provide written informed consent
• Supervisor approval

Exclusion Criteria:

• Known history of allergy or hypersensitivity to potato, potato components or potato products
• Known history of allergy to hepatitis B vaccine in any form or to components of hepatitis B vaccine
• Pregnancy or breast feeding
• Current anti-HBS levels greater than 115 mIU/mL
• Known immunodeficiency, cancer, or use of immunosuppressive medication including cancer chemotherapy and systemic steroids (excluding intermittent use of topical steroids)
• Participation in another investigational study within 30 days of enrollment in this study
• Known and currently active gastrointestinal disease including any of the following: peptic ulcer disease, gastroesophageal reflux, inflammatory bowel disease, diverticulitis, or pancreatitis
• Use of prescription medication or over the counter H2 blockers or proton pump inhibitors (PPIs) for any of the above diseases regularly and within 1 month of enrollment
• Diagnosis of insulin-dependent diabetes or multiple sclerosis
• Significant laboratory abnormality which suggests dysfunction of hematological, renal, or hepatic systems
• Known history of hepatitis B infection in the past
• Temporary exclusion for mild upper respiratory illness, gastrointestinal illness, or other febrile episode that is expected and documented to resolve