SARS-CoV-2-specific cellular immunity, defined as a subject having more than 50 IFN-γ producing SARS-CoV-2-specific cells per 106 PBMC, was observed in 85.7% (13/14) of subjects classified as having a short duration of COVID-19 symptoms, while 94.7% (18/19) of subjects with a long duration of COVID-19 symptoms exhibited a positive response (Table 2). Here, IFNG is linked to COVID-19.