The IGRA approach using a recombinant S protein from SARS-CoV-2 in a whole blood model has been shown to effectively differentiate individuals affected by COVID-19 from those not exposed to the virus, suggesting a promising assay assess the IFN-γ production by SARS-CoV-2-specific T cells in different scenarios of natural infection, vaccine or hybrid immunity. The gene discussed is IFNG; the disease is infection.