Group A had the highest median concentration of T cell-derived IFN-γ, followed by groups B, C, and D. The IFN-γ concentration in group A (median = 560.9 mIU/mL) was significantly higher than that of group C (median = 230.8 mIU/mL; p = 0.0003) or D (median = 187.9 mIU/mL; p = 0.0027), suggesting a potential synergism between DTP and CoronaVac vaccinations to generate COVID-19-specific T cell immunity in these pediatric subjects. Here, IFNG is linked to COVID-19.