IFNG and COVID-19: Aside from overall higher T-cell response rates, heVac KTRs also showed significantly higher (individual) numbers of spike S1- and S2-reactive IFN-γ, IL-2, and bi-functional IFN-γ/IL-2 secreting cells (S1, IFN-γ: P = 0.0042, IL-2: P = 0.0019, IFN-γ/IL-2: P = 0.0019 and S2, IFN-γ: P = 0.0017, IL-2: P = 0.0039, IFN-γ/IL-2: P = 0.0031, respectively) after receiving two doses of COVID-19 vaccines (Figure 2A).