This is a Phase 1b, randomized study in healthy younger (18-50 years) and older (51-70 years) adults to evaluate the safety, tolerability, and immunogenicity of a prime-boost vaccination regimen with an investigational plasmid DNA vaccine directed towards the 2011/12 influenza vaccine strains as a prime followed 36 weeks later by the 2012/13 influenza trivalent inactivated vaccine (TIV) as the booster injection, as compared to placebo prime followed by the 2012/13 seasonal TIV. The hypothesis is that the DNA vaccine will be safe for human administration and that the DNA vaccine prime-TIV boost schedule will elicit a better immune response than the seasonal TIV alone.

Vaccines are an effective way of preventing influenza infection and transmission in humans. Although licensed influenza vaccines are available, ways to improve influenza vaccines continue to be studied. Annually, the World Health Organization (WHO) and the U.S FDA make recommendations on the composition of the seasonal influenza vaccine, with recommendations for the Northern Hemisphere (NH) and for the Southern Hemisphere (SH) considered at different times based on epidemiology data. The annually licensed influenza vaccines consist of 3 components: an Influenza A (H1N1) strain, an Influenza A (H3N2) strain, and an influenza B strain. The current U.S. FDA-licensed influenza vaccines depend upon labor-intensive methods that limit manufacturing capacity and which do not induce broad immune responses to various strains of influenza. The vaccine composition requires frequent adjustment for emerging influenza strains.

The need for influenza vaccines that are more immunogenic and able to induce a more universal immune response against a broad spectrum of influenza strains is well recognized. Earlier laboratory and clinical studies together suggest that an investigational DNA vaccine encoding for the influenza hemagglutinin protein(HA DNA vaccine) administered as a prime, followed by a boost with a traditional inactivated influenza vaccine, may induce a stronger immune response against various influenza strains and with improved durability. The interval of time between the prime vaccination and the boost vaccination is important for the strength of the immune response.

This clinical trial will evaluate the safety, tolerability and immune responses to the investigational HA DNA vaccine prime-TIV boost schedule compared to a placebo prime-TIV boost schedule when the time between the prime and boost is 36 weeks.

Inclusion Criteria:

• 18 to 70 yrs
• Available for clinical follow-up through Study Week 60
• Able and willing to complete the informed consent process
• Willing to donate blood for sample storage to be used for future research
• Physical exam and lab results without clinically significant findings and a Body Mass Index (BMI) <40 within the 70 days prior to enrollment
• Has received the 2011/2012 licensed influenza vaccine 8 or more weeks prior to enrollment and agrees to receive the 2012/2013 TIV as part of study participation

Laboratory Criteria within 70 days prior to enrollment:

• Hemoglobin within institutional normal limits
• White blood cells either within institutional normal range or site physician approves as consistent with healthy adult status
• Platelets = 125,000 - 500,000/mm3
• Alanine aminotransferase (ALT) ≤ 2.5 x upper limit of normal (ULN)
• Serum creatinine ≤ 1 x ULN based on site institutional normal range

Criteria applicable to women of childbearing potential:

• Negative pregnancy test (urine or serum) on day of enrollment
• Agree to use an effective means of birth control from 21 days prior to enrollment through 12 weeks after the first study vaccination

Exclusion Criteria:

Women Specific:

• Breast-feeding or planning to become pregnant during the 12 weeks after enrollment in the study

Subject has received any of the following substances:

• More than 10 days of systemic immunosuppressive medications or cytotoxic medications within the 12 weeks prior to enrollment or any within the 14 days prior to enrollment
• Blood products within 16 weeks prior to enrollment
• Immunoglobulin within 8 weeks prior to enrollment
• Investigational research agents within 28 days (4 weeks) prior to enrollment
• Allergy treatment with antigen injections, unless on maintenance schedule and allergy shots could be staggered with the study vaccinations, within 14 days (2 weeks) prior to enrollment
• Current anti-tuberculosis prophylaxis or therapy

History of any of the following clinically significant conditions:

• Contraindication to receiving an FDA-approved seasonal influenza vaccination
• Serious reactions to vaccines that preclude receipt of study vaccinations, as determined by the site investigator
• Hereditary angioedema, acquired angioedema, or idiopathic forms of angioedema
• Asthma that is severe, unstable or required emergent care, urgent care, hospitalization or intubation during the previous two years or that is expected to require the use of oral, intravenous or high dose inhaled corticosteroids
• Diabetes mellitus type I
• Thyroid disease that is not well-controlled
• Generalized idiopathic urticaria within the 1 year prior to enrollment
• Hypertension that is not well controlled
• Bleeding disorder diagnosed by a doctor (e.g. factor deficiency, coagulopathy, or platelet disorder requiring special precautions), or significant bruising or bleeding difficulties with intramuscular (IM) injections or blood draws, or use of blood thinners such as Coumadin or Plavix®.
• Malignancy that is active or treated malignancy for which there is not reasonable assurance of sustained cure or malignancy that is likely to recur during the period of the study
• Seizure disorder other than: 1) febrile seizures, 2) seizures secondary to alcohol withdrawal more than 3 years ago, or 3) seizures for which no treatment has been required within the 3 years prior to enrollment
• Asplenia, functional asplenia or any condition resulting in the absence or removal of the spleen
• Guillain-Barré Syndrome
• Psychiatric condition that precludes compliance with the protocol; past or present psychoses; disorder requiring lithium; or within 5 years prior to enrollment, a history of suicide plan or attempt
• Any medical, psychiatric, or other condition that, in the judgment of the investigator, is a contraindication to protocol participation or impairs ability to give informed consent