IFNG and COVID-19: Regarding T-cell immunity analyses, it is also worth noting the variety of platforms that have been used for measuring SARS-CoV-2-S-T-cell responses following COVID-19 vaccination in either whole blood or isolated peripheral blood mononuclear cells, including flow cytometry methods for intracellular cytokine (IFN-γ) staining (ICS), such as in the current study, flow cytometry for activation-induced markers (AIM), ELISpot, and IFN-γ-release assays (IGRAs), such as the SARS-CoV-2 Quantiferon® test (QF).