Immunogenicity and safety study of a single dose of SpikoGen® vaccine as a heterologous or homologous intramuscular booster following a primary course of mRNA, adenoviral vector or recombinant protein COVID-19 vaccine in ambulatory adults
Date
2025
Authors
Honda Okubo, Y.
Sajkov, D.
Wauchope, B.
Turner, J.V.
Vote, B.
Antipov, A.
André, G.
Lebedin, Y.
Petrovsky, N.
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Journal article
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Vaccine, 2025; 49(126744):1-11
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Abstract
Background: SpikoGen® is a subunit recombinant Wuhan spike protein produced in insect cells and formulated with Advax-CpG55.2™ adjuvant. It is approved for adult and pediatric use in the Middle East. This study tested the safety and immunogenicity of SpikoGen® as a 3rd, 4th or 5th dose booster following a primary immunisation course of mRNA, adenovirus or SpikoGen® vaccine.
Methods: The trial recruited participants who had received a previous doses of COVID-19 vaccine more than 3 months prior. Each received a single intramuscular booster dose of SpikoGen® vaccine. Spike and nuclear protein antibody levels were measured at 1 and 3 months post-booster, together with collection of data on SARS-CoV-2 breakthrough infections and symptoms of long COVID.
Results: One-month post-booster, anti-spike IgG, sVNT, and pVNT levels were increased in all groups and there was ∼4-fold neutralizing antibodies against the heterologous Omicron BA.2 and BA.4/5 strains. The SpikoGen®-prime group had the highest levels of anti-spike IgG3, consistent with the Advax-CpG adjuvant driving IgG3 induction. There was no effect of age on the vaccine response. The booster dose was well tolerated with no vaccine-associated serious adverse events. Nine participants (9/74, 12.2 %) had a breakthrough SARS-CoV-2 infection between 2 weeks and 3 months post-booster. No long COVID was observed after breakthrough infections. Breakthrough infection was negatively correlated with baseline anti-nuclear protein IgG seropositivity.
Conclusion: A single SpikoGen® booster was well tolerated and stimulated cross- antibody responses against Omicron variants, regardless of the primary vaccine course received. With SARS-CoV-2 variants continuing to evolve, ongoing research is needed into optimum booster strategies.
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Copyright 2025 Elsevier