LAUSR

Significance While making virus-specific immune responses to SARS-CoV-2, residual B and T cell diversity are key to making responses to concurrent co-infections and/or cancers. We applied an antigen receptor–sequencing technology and provide a comprehensive description of the global immune repertoire in hospitalized and nonhospitalized individuals infected with SARS-CoV-2. Although B cell diversity predictably narrowed, significant narrowing of αβ and γδ T cell diversity was unexpectedly observed only in those aged over 50, which is a major inflexion point for COVID-19–associated mortality. Such a discrepancy in how older persons mount T cell responses to a new virus may be considered a risk factor for the elderly, particularly vis-à-vis new virus variants against which T cell immunity may be particularly important.