In a small feasibility study involving 16 participants who underwent QuantiFERON SARS-CoV-2 research use only (QFN SARS-CoV-2) IGRA (interferon-gamma release assay) and QIAreach Anti-SARS-CoV-2 total (anti-CoV-2) test, Jaganathan et al. reported that CD4+ and CD8+ T cell-mediated responses against SARS-CoV-2 were demonstrable in vaccinated subjects as well as in those who had recovered from natural infection [4]. Here, IFNG is linked to infection.