IFNG and COVID-19: As expected, healthy controls naive to COVID-19 also had lower expression of T cell IFN-γ in response to SPIKE peptides in vitro (Figure S3). On the other hand, measurement of PD-1 in COVID+ patients showed that aged participant PBMCs contained higher proportions of PD-1-expressing cells in response to SPIKE as compared to subjects age ≤ 60 (Figures 2A, B; x axis).