Safety and immunogenicity of SpiN-Tec, a T-cell based RBD-Nucleocapsid chimeric vaccine for COVID-19

The SpiN-Tec MCTI UFMG is a chimeric recombinant protein (SpiN) containing the RBD region from the Spike protein (S) fused with the Nucleocapsid protein (N), adjuvanted with a squalene-based emulsion (CTVad1), which was developed as booster COVID-19 vaccine. This is a phase I clinical trial to evaluate safety and reactogenicity. Thirty-six healthy adults aged 18-54, previously vaccinated with two doses of CoronaVac™ (Sinovac) and a booster with the Comirnaty™ Bivalent BA.4/BA.5 (Pfizer-BioNTech), were randomized to receive either SpiN-Tec (20 μg, 60 μg, or 100 μg) or CoviShield™(AstraZeneca). SpiN-Tec was safe and showed a reactogenic profile comparable to CoviShield. Immunogenicity results showed a dose-dependent increase in IgG levels against N and SpiN, peaking at day 28 post-vaccination and declining by day 180. Neutralizing antibody levels against both the Wuhan ancestral and BA1.88 strains showed similar curves presenting no differences between SpiN-Tec and CoviShield. Importantly, SpiN-Tec induced robust IFN-γ production up to 270 days, particularly by CD4⁺ effector memory T cells, indicating a durable immune response memory. These results indicate the potential of SpiN-Tec as a viable COVID-19 booster vaccine.