IFNG and COVID-19: After stimulation with controls and peptide pools spanning SARS-CoV-2 wt and Delta spike proteins, interferon gamma (IFN-γ) and interleukin 2 (IL-2) mRNA levels in total cellular RNAs were measured with RT-qPCR from PBMC samples of 15 vaccinees, 10 COVID-19 patients, and 10 negative controls.