SOLVE: Sustainable Covid-19 Vaccination for Long-term Vaccine Immunity and Effectiveness

SOLVE is An open-label randomized multicentre Experimental Medicine multicenter Trial to evaluate the safety and immunogenicity of experimental versus authorized SARS-CoV-2 vaccine candidates as a booster dose in healthy participants previously vaccinated with authorized mRNA SARS-CoV-2 vaccines. 60 healthy adults participants (12 healthy participants included per group): Group 1: Boost with CD40.RBDv vaccine adjuvanted with Hiltonol® Group 2: Boost with CD40.Pan.CoV vaccine adjuvanted with Hiltonol® Group 3: Boost with MVA-CoV2-S(3P) vaccine Group 4: Boost with Comirnaty® JN.1 vaccine Group 5: Boost with Nuvaxovid™ JN.1 vaccine Primary safety objective : To determine the safety and reactogenicity of a booster injection between D0 and W4. Co-primary immunogenicity objective: To determine the humoral immune response (neutralizing antibody titers, NeutAbs) induced by a booster vaccine at W4 and W48 (for durability).