Inclusion Criteria:

Subjects must meet all of the following inclusion criteria to participate in this study:

• Male or non-pregnant female (as indicated by a negative urine pregnancy test immediately prior to vaccine administration) between the ages of 18 and 40 years, inclusive.
• Women of childbearing potential who are at risk of becoming pregnant must agree to practice adequate contraception (i.e., barrier method, abstinence, and licensed hormonal methods) for at least 3 months after receipt of dose 2 (or dose 3, if applicable).
• Is in good health, as determined by vital signs (heart rate, blood pressure, oral temperature), medical history and a targeted physical examination based on medical history.
• Able to understand and comply with planned study procedures.
• Provides informed consent prior to any study procedures and is available for all study visits.
• Is not receiving any regular medications with the exceptions of birth control pills and vitamins.
• Meets all other inclusion criteria and must have received two doses of inactivated influenza A/H5N1 vaccine in the present study to be eligible for a third dose.

Exclusion Criteria:

Subjects who meet any of the following exclusion criteria at baseline will be excluded from study participation:

• Has a known allergy to eggs or other components of the vaccine.
• Has a positive urine pregnancy test prior to vaccination (if female of childbearing potential), is lactating, or has the intention to become pregnant within 3 months of receipt of their second dose of vaccine.
• Is undergoing immunosuppression as a result of an underlying illness or treatment.
• Has an active neoplastic disease or a history of any hematologic malignancy.
• Is using oral or parenteral steroids, high-dose inhaled steroids (>800 mcg/day of beclomethasone dipropionate or equivalent) or other immunosuppressive or cytotoxic drugs.
• Has a history of receiving immunoglobulin or other blood product within the 3 months prior to enrollment in this study.
• Has received any other licensed vaccines within 2 weeks (for inactivated vaccines) or 4 weeks (for live vaccines) prior to enrollment in this study.
• Has an acute or chronic medical condition that, in the opinion of the investigator, would render vaccination unsafe or would interfere with the evaluation of responses (this includes, but is not limited to: known chronic liver disease, significant renal disease, unstable or progressive neurological disorders, diabetes mellitus, and transplant recipients).
• Has a history of severe reactions following immunization with contemporary influenza virus vaccines.
• Has an acute illness, including an oral temperature greater than 100.4 Fahrenheit, within 1 week of vaccination.
• Received an experimental agent (vaccine, drug, biologic, device, blood product, or medication) within 1 month prior to each vaccination in the study, or expects to receive an experimental agent within 1 month after each vaccination in the study.
• Prior receipt of influenza A/H5N1 vaccine, other than the present study.
• Is enrolled or planning to enroll in another interventional trial at any time between receipt of the third dose of vaccine and the end of the study (approximately 6 months after receipt of the third dose).
• 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.