Safety, reactogenicity, and immunogenicity of a viral vector vaccine against influenza A: Phase I open clinical trial

INTRODUCTION. The development of universal influenza vaccines based on conserved influenza virus antigens is a promising strategy for preventing pandemic influenza. Recombinant vaccines based on adenoviral vectors have high antiviral potential and have proven their effectiveness during the COVID-19 pandemic. In this regard, the development and clinical evaluation of a viral vector vaccine against influenza A seem relevant.

AIM. The aim was to evaluate the safety, reactogenicity, and immunogenicity of a broad-spectrum viral vector vaccine against influenza A after a single intranasal administration in healthy volunteers.

MATERIALS AND METHODS. This clinical trial studied the GamFluVac recombinant human adenovirus serotype 5 (rAd5)-based vaccine against influenza A (National Research Center for Epidemiology and Microbiology named after the honorary academician N.F. Gamaleya). The clinical trial enrolled 36 volunteers. The follow-up period was 28 days. The safety assessment of the viral vector vaccine was based on the incidence, nature, and severity of adverse events (AEs) after a single intranasal administration at doses of 2.5×10¹⁰ (Group 1), 1.0×10¹¹ (Group 2), and 2.5×10¹¹ (Group 3) viral particles. Immunogenicity was evaluated by measuring serum IgG antibodies against influenza A (H5N2) by enzyme immunoassay on Day 0 and Day 28.
RESULTS. No serious or severe AEs were reported during the clinical trial. Most AEs associated with the vaccine manifested as respiratory disorders, abnormal blood findings, and general disorders (elevated body temperature, headache, chills, malaise, arthralgia, and myalgia). Statistically significant differences (p=0.0285) were identified in the incidence of general disorders and administration site conditions in Group 1 (0%), Group 2 (16.7%), and Group 3 (33.3%). Group 3 demonstrated the highest increase in the geometric mean titres of specific IgG antibodies (2.8 times the baseline) on Day 28. In this group, 100% of volunteers had a ≥2-fold seroconversion rate, and 41.7% of volunteers had a ≥4-fold seroconversion rate.

CONCLUSIONS. This phase I clinical trial of the GamFluVac viral vector vaccine against influenza A demonstrated the immunogenicity and favourable safety profile of the vaccine after a single intranasal administration.

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