The purpose of this study is to evaluate the immunogenicity and safety of inactivated subunit H5N1 influenza vaccine in individuals who have previously received live attenuated H2N2, H6N1, or H9N2 influenza vaccine, as well as in individuals who have never previously received H5N1 or other pandemic live attenuated influenza vaccines.

This study will evaluate the immunogenicity and safety of inactivated subunit H5N1 influenza vaccine in individuals who have previously received live attenuated H2N2, H6N1, or H9N2 influenza vaccine, as well as in individuals who have never previously received H5N1 or other pandemic live attenuated influenza vaccines (pLAIVs).

Participants will be enrolled in two cohorts. Cohort 1 will include participants who received two doses of live attenuated H2N2, H6N1, or H9N2 influenza vaccine during a prior Center for Immunization Research (CIR) study; Cohort 2 will include participants who have never previously received a pLAIV. Participants in both cohorts will receive one dose of H5N1 pISV vaccine by injection at Day 0.

Participants will attend study visits on Days 0, 7, 14, 28, 56, 90, and 360. Study visits may include a physical examination, medical history, and blood and urine collection. All participants will be followed for approximately 360 days after receiving the H5N1 pISV vaccine.

Inclusion Criteria:

• Adult males and non-pregnant females between 18 years and 60 years of age inclusive.

• General good health, without significant medical illness, physical examination findings, or significant laboratory abnormalities as determined by the investigator.

• Available for the duration of the trial.

• Able to demonstrate understanding of key study concepts, study rationale, and study participation requirements by scoring greater than or equal to 70% on a written comprehension assessment in 3 or fewer attempts.

• Willingness to participate in the study as evidenced by signing the informed consent document.

• Willingness to allow storage and testing of laboratory samples for future research.

• Received 2 doses of live attenuated H2N2, H6N1, or H9N2 vaccine in a prior trial (Cohort 1) or H2N2, H6N1 and H9N2 naïve (Cohort 2)

• Willingness to forego seasonal influenza virus vaccination from 1 month before vaccination until 3 months after vaccination.

• Female subjects of childbearing potential must agree to have used effective birth control methods beginning at least one month prior to vaccination, and continuing with 'per label/fully effective use' for the chosen method for duration of the study, from amongst these:

  • pharmacologic/hormonal contraceptives, including oral, parenteral, subcutaneous, and transcutaneous delivery;
  • condoms with spermicide;
  • diaphragm with spermicide;
  • intrauterine device;
  • absolute abstinence from heterosexual intercourse as a matter of normal preferred lifestyle;
  • or must be surgically sterile or must be age 50 AND have had no menses at all for at least one full year.
  • All females must provide urine for pregnancy testing prior to enrollment (immediately prior vaccination), as well as a statement of menstrual history and a summary of all potentially reproductive sexual activity for the month prior to vaccination, and at each study contact throughout the study, and report known or suspected pregnancy immediately.

• Willingness to refrain from blood donation during the course of the study.

Exclusion Criteria:

• Pregnancy as determined by a positive test for human choriogonadotropin (beta-HCG), an indicator of pregnancy or history of recent unprotected intercourse in a woman of reproductive capacity.

• Currently breast-feeding.

• Evidence of clinically significant neurologic, cardiac, pulmonary, hematologic, hepatic, rheumatologic, autoimmune, or renal disease by history, physical examination, and/or laboratory studies.

• Behavioral or cognitive impairment or psychiatric disease that in the opinion of the investigator affects the ability of the subject to understand and cooperate with the study protocol.

• Have medical, occupational, or family problems as a result of alcohol or illicit drug use during the past 12 months.

• Other condition that in the opinion of the investigator would jeopardize the safety or rights of a subject participating in the trial or would render the subject unable to comply with the protocol.

• History of anaphylaxis in response to any vaccine or vaccine component.

• History of life-threatening reaction to prior influenza vaccine.

• Positive enzyme-linked immunosorbent assay (ELISA) and confirmatory test for human immunodeficiency virus type 1 (HIV-1).

• Positive ELISA and confirmatory test (e.g., HCV RNA PCR) for hepatitis C virus (HCV).

• Positive hepatitis B virus surface antigen (HBsAg) by ELISA.

• Known immunodeficiency syndrome or history suggestive of impaired immune function.

• History of Guillain-Barré syndrome.

• Use of chronic oral or intravenous administration (greater than or equal to 14 days) of immunosuppressive doses of steroids, i.e., prednisone greater than 10 mg per day, immunosuppressants or other immune-modifying drugs within 30 days of starting this study.

• Receipt of a live vaccine within 4 weeks or a killed vaccine within 2 weeks prior to study vaccination.

• Receipt of blood or blood-derived products (including immunoglobulin) within 6 months prior to study vaccination.

• Receipt of another investigational vaccine or drug within 30 days prior to study vaccination.

• In addition to the above, participants in Cohort 1 (pandemic live attenuated influenza vaccine [pLAIV] recipients) and Cohort 2 (naïve cohort) must also not experience any of the following:

  • Previous enrollment in an H5N1 influenza vaccine trial.

• Participants in Cohort 2 (naïve cohort) will be excluded if they are:

  • Seropositive to the H5N1 influenza A virus (serum hemagglutination inhibition assay (HAI) titer greater than 1:8).
  • Have previously received an investigational live attenuated influenza vaccine (LAIV) in another study.