Avian influenza (AI), also known as bird flu, has become a major public health concern in many regions of the world. The purpose of this study is to evaluate the safety of and immune response to an AI vaccine in healthy adults.

AI is caused by a virus that occurs naturally among birds. Because the virus has the ability to mutate into a form that can efficiently spread among the human population, AI has the potential to cause pandemics. The purpose of this study is to evaluate the safety of and immune response to the AI vaccine H9N2 (6-2) AA ca Reassortant (A/Chicken/Hong Kong/G9/97 x A/Ann Arbor/6/60 ca) in healthy adults who have never been exposed to the H9N2 virus.

This study will last from approximately 6 weeks, up to a maximum of approximately 20 weeks. Participation includes a 10-day minimum hospital stay in an isolation unit of the Bayview Medical Center of Johns Hopkins University. Participants will be admitted to the isolation unit 2 days prior to vaccination. At vaccination, participants will be given one dose of the H9N2 (6-2) AA ca Reassortant (A/Chicken/Hong Kong/G9/97 x A/Ann Arbor/6/60 ca) vaccine in the form of nose drops. Each day for the next 7 days, participants' vital signs will be monitored and nasal washes will be collected to test for the presence of vaccine virus. Participants may be discharged from the hospital after 3 consecutive negative viral cultures, but not before Day 7 after vaccination. Follow-up visits will occur on Days 21, 28, and 42, and will include blood collection and a physical exam.

Participants who received the first dose of the (A/Chicken/Hong Kong/G9/97 x A/Ann Arbor/6/60 ca) vaccine will be asked to receive a second dose of the vaccine 4 to 12 weeks after receiving the initial dose. Study procedures will be identical to those related to the first vaccination.

Inclusion Criteria:

• Born after 1968
• Good general health
• Available for the duration of the study
• Female participants must agree to use acceptable forms of contraception

Exclusion Criteria:

• Significant medical illness, physical examination findings, or urine or blood abnormalities
• Clinically significant neurologic, heart, lung, liver, rheumatologic, autoimmune, or kidney disease
• Behavioral, cognitive, or psychiatric disease that, in the opinion of the investigator, may interfere with the study
• Previously enrolled in an H9N2 influenza vaccine study or in any other study of a bird flu vaccine
• Positive for the H9N2 influenza A virus (serum hemagglutination inhibiting [HI] factor antibody titer greater than 1:8)
• Medical, work, or family problems as a result of alcohol or illegal drug use within 12 months prior to study entry
• History of severe allergic reaction or anaphylaxis
• Current asthma or reactive airway disease within 2 years prior to study entry
• History of Guillain-Barre syndrome
• HIV-1 serotype positive
• Hepatitis C virus (HCV) positive
• Hepatitis B surface antigen positive
• Known immunodeficiency syndrome
• Use of corticosteroids or immunosuppressive drugs within 30 days prior to study entry. Participants who have used topical corticosteroids are not excluded.
• Live vaccine within 4 weeks prior to study entry
• Killed vaccine within 2 weeks prior to study entry
• Absence of spleen
• Blood products within 6 months prior to study entry
• Current smoker unwilling to stop smoking for the duration of the study
• Plans to travel to the Southern Hemisphere or Asia within 14 days prior to study entry
• Plans to travel on a cruise ship within 14 days prior to study entry
• Work in the poultry industry
• Received an investigational agent within 30 days prior to study entry
• 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 participation in the study
• Pregnancy or breastfeeding