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SARS-CoV-2 has been identified as the causative agent of a global outbreak of respiratory tract disease (COVID-19). In some patients, the infection results in moderate to severe acute respiratory distress syndrome, requiring invasive mechanical ventilation. High serum levels of IL-6 and IL-10, and an immune hyperresponsiveness referred to as a “cytokine storm,” have been associated with poor clinical outcome. Despite the large numbers of COVID-19 cases and deaths, information on the phenotype and kinetics of SARS-CoV-2–specific T cells is limited. Here, we studied 10 patients with COVID-19 who required admission to an intensive care unit and detected SARS-CoV-2–specific CD4⁺ and CD8⁺ T cells in 10 of 10 and 8 of 10 patients, respectively. We also detected low levels of SARS-CoV-2–reactive T cells in 2 of 10 healthy controls not previously exposed to SARS-CoV-2, which is indicative of cross-reactivity …