Figure 3.

Schematic of vaccination schedule: S1-CpG, S1-alum, S1 intranasal, S1 subcutaneous, saline intranasal, or subcutaneous administration. Mice received vaccines or control solutions intranasally four times on days 0, 7, 14, and 21. On day 42, the vaccinated mice were euthanized, and blood was collected for anti-RBD/S1 titer measurement. Mice received vaccines or control solutions subcutaneously twice on days 0 and 28. On day 56, the vaccinated mice were euthanized, and blood was collected for anti-RBD/S1 titer measurement. (a) Anti-S1 IgG titers in 1:1000 diluted serum. (b) Anti-RBD IgG titers in 1:1000 diluted serum. The closed circles show the individual data. The bars represent the median. * p < 0.05, ** p < 0.01 compared to all other groups. OD₄₅₀, optical density measurements at 450 nm. RBD, receptor-binding domain; i.n., intranasal; s.c., subcutaneous. Samples with OD values ≥ 2.5 are deemed unaffected in relation to statistical outcomes.