Fig. 1.

Study design of immunogenicity of a SARS-CoV-2 spike subunit protein against COVID-19. Six mice per group were injected with either two intramuscular doses of SARS-CoV-2 S-protein alone or one intramuscular dose of AlPO₄- or SQ@NP-adjuvanted SARS-CoV-2 S-protein. At Week 12, all mice were boosted i.m. with the same vaccine formulations as priming injection. Sera and spleen collection were performed to determine the B- and T-cell responses.