PSMD1 and infection: The data revealed that 2xVacc+δ, 3xVacc, 3xVacc+ο, and 3xVacc+δ groups had significantly higher S1-specific IgG titers compared to the 2xVacc group and the groups with an alpha breakthrough infection; 2xVacc+α, 3xVacc+α (Fig. 1b).