IFNG and COVID-19: Generally, COVID-19 vaccine candidates have induced low T cell responses in mice, with IFNγ+ responses of 0 to 2% and 0 to 1% among CD8+ and CD4+ T cells, respectively (43, 44), or 1000 to 2000 SFCs/1 × 106 splenocytes by IFNγ ELISpot (19, 44, 45).