Inclusion Criteria:

• The subject must have previously received at least 2 doses via the intramuscular route of placebo or vaccine derived from A/H5N1/VN/1203/04 as part of one of the following DMID Protocol Nos.: 04-062, 04-063 (and 05-0090), 04-076, 05-0015, 05-0127, 05-0141, or 06-0089; or the subject must have received placebo intramuscularly as part of DMID Protocol No. 06-0052.
• The subject must be 19 years old or older.
• Women of childbearing potential (not surgically sterile via tubal ligation, bilateral oophorectomy or hysterectomy or who are not postmenopausal for greater than or equal to 1 year) must agree to practice adequate contraception, including, but not limited to, abstinence, monogamous relationship with vasectomized partner, barrier methods such as condoms, diaphragms, spermicides, birth control pills, patches or hormonal shots or hormonal implants, NuvaRing and IUDs (intrauterine devices), during the study period between enrollment and 30 days following receipt of the last dose of vaccine.
• For a female subject of childbearing potential, she must have a negative pregnancy test (urine or serum) within 24 hours prior to vaccination.
• The subject is in good health, as determined by vital signs (heart rate less than 100 bpm; blood pressure: systolic greater than or equal to 90 mm Hg and less than or equal to 140 mm Hg; diastolic less than or equal to 90 mm Hg; oral temperature less than 100.0 degrees F), medical history to ensure stable medical condition, and a targeted physical examination, when necessary, based on medical history. A systolic blood pressure of less than or equal to 160 and a diastolic blood pressure of less than or equal to 90 is acceptable in subjects greater than 65 years of age.
• The subject is able to understand and comply with the planned study procedures, including being available for all study visits.
• The subject has provided informed consent prior to any study procedures.

Exclusion Criteria:

• The subject is allergic to eggs, egg products, chicken or egg proteins or other components of the vaccine (including gelatin, formaldehyde, octoxinol and thimerosal).
• The subject is a woman who is breastfeeding or intends to become pregnant during the study period between enrollment and 30 days following receipt of the last dose of vaccine.
• The subject is immunosuppressed as a result of an underlying illness or treatment with immunosuppressive or cytotoxic drugs, or use of anticancer chemotherapy or radiation therapy within the preceding 36 months.
• The subject has an active neoplastic disease (excluding non-melanoma skin cancer or prostate cancer that is stable in the absence of therapy) or a history of any hematologic malignancy. An active neoplastic disease is defined as treatment for neoplastic disease within the past 5 years.
• The subject has long-term (greater than 2 weeks) use of oral or parenteral glucocorticoids, or high-dose inhaled steroids (>800 mcg/day of beclomethasone dipropionate or equivalent) within the preceding 6 months (nasal and topical steroids are allowed).
• The subject received immunoglobulin or another blood product within the 3 months prior to enrollment in this study.
• The subject has received an inactivated vaccine within the 2 weeks or a live vaccine within the 4 weeks prior to enrollment in this study or plans to receive another vaccine within the next 28 days (or 56 days for prior placebo recipients).
• The subject has an acute or chronic medical condition that would render vaccination unsafe or would interfere with the evaluation of responses. These conditions include, but are not limited to: solicited reactogenicity symptoms, history of significant renal impairment (dialysis and treatment for kidney disease, including diabetic and hypertensive kidney disease); subjects with diabetes mellitus, well-controlled with oral agents may enroll as long as there has been no dose adjustment with the past 6 months; insulin-dependent diabetes is excluded; cardiac insufficiency, if heart failure is present (New York Association Functional Class III or IV); an arteriosclerotic event during the 6 months prior to enrollment (e.g., history of myocardial infarction, stroke, recanalization of femoral arteries or transient ischemic attack).
• The subject has a history of a severe reaction following receipt of an influenza virus vaccine.
• The subject has an acute illness or an oral temperature greater than 99.9 degrees F (37.7 degrees C) within 3 days prior to enrollment or vaccination.
• The subject is currently participating in a study that involves an experimental agent (vaccine, drug, biologic, device, blood product, or medication) or has received an experimental agent within 1 month prior to enrollment in this study, or expects to receive another experimental agent during participation in this study.
• The subject has any condition that would, in the opinion of the site investigator, place the subject at an unacceptable risk of injury or render the subject unable to meet the requirements of the protocol.
• The subject has a diagnosis of schizophrenia, bi-polar disease, or other severe (disabling) chronic psychiatric diagnosis.
• The subject has been hospitalized within the past 5 years prior to enrollment for psychiatric illness, history of suicide attempt or confinement for danger to self or others.
• The subject is receiving psychiatric drugs. Subjects who are receiving a single antidepressant drug and are stable for at least 3 months prior to enrollment without decompensating are allowed enrollment into the study.
• The subject has a history of alcohol or drug abuse in the 5 years prior to enrollment.
• The subject has a known human immunodeficiency virus, hepatitis B, or hepatitis C infection.
• The subject has a history of Guillain-Barré syndrome.
• The subject has any condition that the investigator believes may interfere with successful completion of the study.

The subject plans to enroll in another clinical trial that has a study intervention such as a drug, biologic, or device that could interfere with safety assessment of the investigational product at any time during the study period.