Avian influenza (AI), or bird flu, has recently become a major health concern in Asia and other parts of the world. The need for a vaccine to prevent the spread of AI among livestock and to humans is sorely needed. The purpose of this study is to test the safety of and immune response to a new AI vaccine in healthy adults.

AI viruses in their natural reservoir in waterfowl are the source from which novel HA and NA subtypes are introduced into the human population, and have the potential to initiate an influenza pandemic. This study will evaluate the safety and immunogenicity of a live, attenuated recombinant AI virus vaccine, H5N1 (6-2) AA Ca Recombinant (A/VietNam/1203/2004 x A/AnnArbor/6/60/Ca).

Participants in this study will receive one or two doses of the vaccine. There are 3 groups in this study:

• Group 1 will receive two vaccinations at the highest dose.
• Group 2 will receive one vaccination at a dose in-between the lowest and highest doses.
• Group 3 will receive one vaccination at the lowest dose.

Group 1 will enroll first, probably in 2006. Groups 2 and 3 will not enroll until it is determined by safety review that the vaccine is well-tolerated and greater than 80% of Group 1 participants shed vaccine virus or develop a specific immune response to the vaccine.

Participation in this study includes a hospital stay in an isolation unit of the Bayview Medical Center of Johns Hopkins University. All participants will receive the vaccine at study entry and will remain in the isolation unit for a minimum of 14 days after vaccination. A physical exam and a nasal wash will occur daily in the isolation unit until a participant is discharged from the hospital. Participants will be allowed to leave the unit once viral cultures for influenza from nasal washes are negative for at least 3 consecutive days beginning on Day 10. Blood collection will occur at study entry, Day 7, sometime between Days 28 and 35, and sometime between Days 56 and 63.

There will be two separate hospitalizations for Group 1 participants. Group 1 participants will receive their doses of vaccine at study entry and sometime between Days 28 and 35. A physical exam and a nasal wash will occur daily in the isolation unit until a participant is discharged from the hospital. Participants will be allowed to leave the unit once viral cultures for influenza from nasal washes are negative for at least 3 consecutive days beginning on Day 10. Blood collection will occur at 4 or 5 selected timepoints, depending on the timing of the second vaccination.

Inclusion Criteria:

• Good general health
• Available for the duration of the trial
• Willing to use acceptable forms of contraception

Exclusion Criteria:

• Clinically significant neurologic, cardiac, pulmonary, hepatic, rheumatologic, autoimmune, or renal disease
• Behavioral, cognitive, or psychiatric disease that, in the opinion of the investigator, affects the ability of the volunteer to understand and cooperate with the study
• Medical, work-related, or family problems as a result of alcohol or illicit drug use in the 12 months prior to study entry
• History of severe allergic reaction or anaphylaxis
• Current asthma or reactive airway disease
• History of Guillain-Barre syndrome
• HIV-1 infected
• Hepatitis C virus infected
• Positive for hepatitis B surface antigen (HBsAg)
• Known immunodeficiency syndrome
• Use of corticosteroids or immunosuppressive drugs within 30 days of study entry. Participants who have used topical corticosteroids are not excluded.
• Live vaccine within 4 weeks of study entry
• Killed vaccine within 2 weeks of study entry
• Absence of spleen
• Blood products within 6 months of study entry
• Current smoker
• Have traveled to the Southern Hemisphere or Asia within 14 days prior to study entry
• Have traveled on a cruise ship within 14 days prior to study entry
• Work in the poultry industry
• Investigational agents within 60 days prior to study entry, or currently participating in another investigational vaccine or drug trial
• Allergy to eggs or egg products
• Purified protein derivative (PPD) positive (positive tuberculosis [TB] test)
• Family member with immunodeficiency
• Other condition that, in the opinion of the investigator, would affect the participant's participation in the study
• Pregnant or breastfeeding