A Safety and Immunogenicity Study of IVACFLU-A/H5N1

The study hypothesis was that two 0.5 mL doses of whole virion monovalent A/H5N1 influenza vaccine (IVACFLU-A/H5N1) adjuvanted with alum would be safe and well tolerated in healthy adults, and that at least one of the two doses tested would be immunogenic in 60% or more of the subjects tested.

Although the A/H1N1 (2009) pandemic has subsided and the virus has become endemic, the threat of another pandemic due to avian influenza A/H5N1 remains constant. Since 1997, highly pathogenic A/H5N1 avian viruses have caused both widespread outbreaks in poultry with high mortality and sporadic, severe, and fatal disease in humans. Southeast Asian countries, including Vietnam, have been affected by influenza A/H5N1. From 2003 through March 2015, WHO has reported 826 confirmed human cases of A/H5N1 influenza infection; including 440 fatal cases (World Health Organization, 2015). Southeast Asian countries accounted for 42% of all confirmed influenza A/H5N1 cases reported since 2003, and influenza A/H5N1 infection in animals is now thought to be endemic in the region (World Health Organization, 2015). As of March 2015, Vietnam has reported 127 confirmed human cases and 64 deaths. In 2014, two cases of A/H5N1 avian influenza were reported in Vietnam. Therefore, the risk of transmission to human is still present.

At the time of the study, no influenza A/H5N1 vaccine had been licensed in Vietnam. IVACFLU-A/H5N1 is an influenza A/H5N1 vaccine produced by Institute of Vaccines and Medical Biologicals (IVAC) using embryonated chicken eggs. IVACFLU-A/H5N1 is a whole virus vaccine, collected in a linear sucrose density gradient solution using a continuous flow centrifuge (Alfa Wassermann, West Caldwell, NJ) and inactivated with formaldehyde. The vaccine is alum adjuvanted. Vaccine strain NIBRG-14 derived from original influenza A/Vietnam/1194/2004 was provided to IVAC by the National Institute for Biological Standards and Control of the Health Protection Agency of the United Kingdom. A clinical trial of IVACFLU-A/H5N1 vaccine conducted in 75 subjects at the Ben Luc Health District in Vietnam in 2014 showed that the vaccine is safe and immunogenic at doses of 7.5 and 15 mcg.

This study was conducted in two stages: Phase 2 was a dose selection study where subjects were randomized to one of the three groups (15 mcg IVACFLU-A/H5N1 vaccine, 30 mcg IVACFLU-A/H5N1 vaccine or placebo) at a 1:1:1 ratio. The conduct of Phase 3 was dependent on showing hemagglutination inhibition (HAI) response titer of ≥1:40 in ≥60% of vaccine recipients in at least one of the two Phase 2 IVACFLU-A/H5N1 vaccine groups. Based on the review of immunogenicity and safety results from the Phase 2 study, a dose of study vaccine was selected for Phase 3. Subjects were randomized at two sites (Khanh Hoa and Hai Phong) to receive the IVACFLU-A/H5N1 vaccine dose selected in Phase 2 or placebo . Safety was assessed in all subjects and immunogenicity was measured in a subset of subjects at the Hai Phong study site.

Eligibility Criteria:
Inclusion Criteria:

* Male or female adult 18 through 60 years of age at the enrollment visit.
* Literate (by self-report) and willing to provide written informed consent.
* Healthy adults, as established by the medical history and screening evaluations, including physical examination, capable and willing to complete Diary Cards, and willing to return for all follow-up visits.
* For females able to become pregnant, willing to utilize reliable birth control measures (intrauterine device, hormonal contraception, condoms) through the Day 43 visit.

Exclusion Criteria:

* Participation in another clinical trial involving any vaccine or therapy within the previous three months, or planned enrollment in such a trial during the period of this study.
* Received any non-study vaccine within 4 weeks prior to enrollment or refused to postpone receipt of such vaccines until after the Day 43 visit.
* Current or recent (within 2 weeks of enrollment) acute illness with or without fever.
* Received immune globulin or other blood products within 3 months prior to study enrollment or planned receipt of such products prior to the Day 43 visit.
* Chronic administration (defined as more than 14 consecutively-prescribed days) of immunosuppressants or other immune-modulating therapy within six months prior to study enrollment. (For corticosteroids, this meant prednisone or equivalent, 0.5 mg per kg per day; topical or intranasal steroids were allowed.)
* History of asthma.
* Hypersensitivity after previous administration of any vaccine.
* Suspected or known hypersensitivity to any of the study vaccine components, including chicken or egg protein, antibiotics, and rubber (from the vaccine vial stoppers).
* Acute or chronic clinically significant pulmonary, cardiovascular, hepatobiliary, metabolic, neurologic, psychiatric, or renal functional abnormality, as determined by medical history, physical examination, or clinical laboratory screening tests (Phase 2 only), which in the opinion of the investigator, might have interfered with the study objectives.
* History of any blood or solid organ cancer.
* History of thrombocytopenic purpura or known bleeding disorder.
* History of seizures.
* Known or suspected immunosuppressed or immune deficient condition of any kind.
* Known Hepatitis B Virus (HBV) or Hepatitis C virus (HCV) infection by self-report (Phase 3) or a positive test for either HBV surface antigen (HBsAg) or HCV antibody using anti-HCV test (Phase 2).
* Known HIV infection (self-report)
* Known active tuberculosis or symptoms of active tuberculosis (self-report).
* History of chronic alcohol abuse and/or illegal drug use.
* Pregnancy or lactation (a negative pregnancy test was required before administration of study product for all women of childbearing potential).
* History of Guillain-Barre Syndrome.
* Any condition in the opinion of the investigator that would have increased the health risk of the subject if he/she participated in the study or interfered with the evaluation of the study objectives.

Note: Minor out-of-range laboratory values no greater than Grade 1 were not considered to be exclusionary at screening.