To determine B15/S919-specific CD8+ T cell responses in COVID-19 patients across disease severities (SI Appendix, Fig. S1A), we analyzed cellular responses of 45 unvaccinated HLA-B*15:01-expressing individuals, either asymptomatic (n = 3), symptomatic but recovering at home (n = 14 mild) or hospitalized (n = 15 moderate, n = 13 severe/critical), with prepandemic/preinfection PBMC samples (n = 14) for comparison. Here, CD8A is linked to COVID-19.