SARS-CoV-2-specific T cell responses wane profoundly in convalescent individuals 10 months after primary infection

A key question in the coronavirus disease 2019(COVID-19)pandemic is the duration of specific T cell responses against the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)post primary infection,which is difficult to address due to the large-scale COVID-19 vaccination and re-exposure to the virus.Here,we conducted an analysis of the long-term SARS-CoV-2-specific T cell responses in a unique cohort of convalescent individuals(CIs)that were among the first to be infected worldwide and without any possible antigen re-exposure since then.The magnitude and breadth of SARS-CoV-2-specific T cell responses correlated inversely with the time that had elapsed from disease onset and the age of those CIs.The mean magnitude of SARS-CoV-2-specific CD4 and CD8 T cell responses decreased about 82%and 76%,respectively,over the time period of ten months after infection.Accordingly,the longitudinal analysis also demonstrated that SARS-CoV-2-specific T cell responses waned significantly in 75%of CIs during the follow-up.Collectively,we provide a comprehensive characterization of the long-term memory T cell response in CIs,suggesting that robust SARS-CoV-2-specific T cell immunity post primary infection may be less durable than previously expected.