A Randomized Clinical Trial of an Inactivated Avian Influenza A (H7N7) Vaccine

<div><h3>Background</h3><p>Concern for a pandemic caused by a newly emerged avian influenza A virus has led to clinical trials with candidate vaccines as preparation for such an event. Most trials have involved vaccines for influenza A (H5N1), A (H7N7) or A (H9N2).</p> <h3>Objective</h3><p>To evaluate dosage-related safety and immunogenicity of an inactivated influenza A (H7N7) vaccine in humans.</p> <h3>Design</h3><p>One hundred twenty-five healthy young adults were randomized to receive two doses intramuscularly of placebo or 7.5, 15, 45 or 90 µg of HA of an inactivated subunit influenza A (H7N7) vaccine (25 per group), four weeks apart. Reactogenicity was evaluated closely for one week and for any adverse effect for six months after each dose. Serum hemagglutination-inhibiting and neutralizing antibody responses were determined four weeks after each dose and at six months.</p> <h3>Results</h3><p>Reactogenicity evaluations indicated the vaccinations were well tolerated. Only one subject developed a ≥4-fold serum hemagglutination-inhibition (HAI) antibody response and a final titer of ≥1∶40 four weeks after dose two and only five subjects developed a neutralizing antibody rise and a final titer of ≥1∶40 in tests performed at a central laboratory. Four of the five were given the 45 or 90 µg HA dosage. A more sensitive HAI assay at the study site revealed a dose-response with increasing HA dosage but only 36% in the 90 µg HA group developed a ≥4-fold rise in antibody in this test and only one of these achieved a titer of ≥1∶32.</p> <h3>Conclusion</h3><p>This inactivated subunit influenza A (H7N7) vaccine was safe but poorly immunogenic in humans.</p> <h3>Trials Registration</h3><p>ClinicalTrials.gov <a href="http://clinicaltrials.gov/ct2/show/NCT00546585">NCT00546585</a></p> </div

Solicited Adverse Events (AE) after Influenza A (H7N7) Vaccinatons.

1<p>As determined in single radial immunodiffusion assays.</p>2<p>Number subjects evaluated.</p

Serum Antibody Responses to Influenza A (H7N7) Vaccinations¹.

1<p>As determined at central laboratory; increase defined as ≥4-fold or <10 to 40.</p>2<p>As determined in single radial immunodiffusion assays.</p>3<p>Number of subjects in evaluation.</p>4<p>Hemagglutination-inhibition (HAI) and neutralizing (neut) antibody assays at central laboratory.</p

Flow diagram of the randomized clinical trial of an inactivated subunit influenza A (H7N7) vaccine.

<p>Flow diagram of the randomized clinical trial of an inactivated subunit influenza A (H7N7) vaccine.</p

Demographics by Study Group.

1<p>Male vs. nonmale frequency by dosage, chi-square 1.73, p = .785.</p>2<p>White vs. nonwhite frequency by dosage, chi-square 7.04, p = .134.</p>3<p>Age vs. dosage, Anova, p>.05.</p

Serum Antibody Responses to H7N7 Vaccinations¹.

1<p>Hemagglutination-inhibition antibody assays at primary study 'site.</p>2<p>As determined in single redial immunodiffusion assays.</p>3<p>Number of subjects in evaluation.</p>4<p>Increasing dosage induced increased % increase; logistic regression, p = .001.</p

Evaluations for in vitro correlates of immunogenicity of inactivated influenza a H5, H7 and H9 vaccines in humans.

BACKGROUND:Serum antibody responses in humans to inactivated influenza A (H5N1), (H9N2) and A (H7) vaccines have been varied but frequently low, particularly for subunit vaccines without adjuvant despite hemagglutinin (HA) concentrations expected to induce good responses. DESIGN:To help understand the low responses to subunit vaccines, we evaluated influenza A (H5N1), (H9N2), (H7N7) vaccines and 2009 pandemic (H1N1) vaccines for antigen uptake, processing and presentation by dendritic cells to T cells, conformation of vaccine HA in antibody binding assays and gel analyses, HA titers with different red blood cells, and vaccine morphology in electron micrographs (EM). RESULTS:Antigen uptake, processing and presentation of H5, H7, H9 and H1 vaccine preparations evaluated in humans appeared normal. No differences were detected in antibody interactions with vaccine and matched virus; although H7 trimer was not detected in western blots, no abnormalities in the conformation of the HA antigens were identified. The lowest HA titers for the vaccines were <1:4 for the H7 vaccine and 1:661 for an H9 vaccine; these vaccines induced the fewest antibody responses. A (H1N1) vaccines were the most immunogenic in humans; intact virus and virus pieces were prominent in EM. A good immunogenic A (H9N2) vaccine contained primarily particles of viral membrane with external HA and NA. A (H5N1) vaccines intermediate in immunogenicity were mostly indistinct structural units with stellates; the least immunogenic A (H7N7) vaccine contained mostly small 5 to 20 nm structures. SUMMARY:Antigen uptake, processing and presentation to human T cells and conformation of the HA appeared normal for each inactivated influenza A vaccine. Low HA titer was associated with low immunogenicity and presence of particles or split virus pieces was associated with higher immunogenicity

Percentage of Subjects Developing Serum Hemagglutination-inhibition Antibody Titers ≥1∶40 (or 1∶32) by Vaccine HA Dosage after Vaccinations with Monovalent Inactivated Influenza A Virus Vaccines.¹

1<p>All are after two doses of subunit vaccine 3–4 weeks apart and all trials were in healthy adults aged 18 to 49 except as noted.</p>2<p>Vaccine subtype and strain.</p>3<p>Manufacturer: SP – Sanofi Pasteur; GSK – GlaxoSmithKline, Wyeth – batch donated to NIAID.</p>4<p>Percents are for clinical trials reporting results for the dosages listed. Dosages are as determined in single radial immunodiffusion assays (SRID).</p>5<p>Data are FDA reanalysis of trial results reported in reference 2.</p>6<p>Data provided by Belshe, RB, et al. (ref 10).</p>7<p>Data are after one dose for ages 18–64 and 18–49 and after two doses for 3–9 and 0.5–3.</p>8<p>Clinical trial results for vaccines used in this study, references 5, 6, 10 were with the USA licensed H5/VN/04 vaccine.</p

Polyacrylamide gels run under reducing and nonreducing conditions for trimeric HA and HA1 and HA2 subunits bound and separate.

<p>Coomassie blue stain was used for protein and western blots with polyclonal antisera for protein identity. Gels are for vaccines (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050830#pone-0050830-g004" target="_blank">Figure 4A</a>) and viruses (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050830#pone-0050830-g004" target="_blank">Figure 4B</a>). Baculovirus expressed H3 HA was used as control (not shown).</p