Background Understanding the T cell response to SARS-CoV-2 is critical to vaccine development, epidemiological surveillance and disease control strategies. This systematic review critically evaluates and synthesises the relevant peer-reviewed and pre-print literature published from 01/01/2020-26/06/2020. Methods For this systematic review, keyword-structured literature searches were carried out in MEDLINE, Embase and COVID-19 Primer. Papers were independently screened by two researchers, with arbitration of disagreements by a third researcher. Data were independently extracted into a pre-designed Excel template and studies critically appraised using a modified version of the MetaQAT tool, with resolution of disagreements by consensus. Findings were narratively synthesised. Results 61 articles were included. 55 (90%) studies used observational designs, 50 (82%) involved hospitalised patients with higher acuity illness, and the majority had important limitations. Symptomatic adult COVID-19 cases consistently show peripheral T cell lymphopenia, which positively correlates with increased disease severity, duration of RNA positivity, and non-survival; while asymptomatic and paediatric cases display preserved counts. People with severe or critical disease generally develop more robust, virus-specific T cell responses. T cell memory and effector function has been demonstrated against multiple viral epitopes, and, cross-reactive T cell responses have been demonstrated in unexposed and uninfected adults, but the significance for protection and susceptibility, respectively, remains unclear. Conclusion A complex pattern of T cell response to SARS-CoV-2 infection has been demonstrated, but inferences regarding population level immunity are hampered by significant methodological limitations and heterogeneity between studies, as well as a striking lack of research in asymptomatic or pauci-symptomatic individuals. In contrast to antibody responses, population-level surveillance of the T cell response is unlikely to be feasible in the near term. Focused evaluation in specific sub-groups, including vaccine recipients, should be prioritised.
【초록키워드】 COVID-19, SARS-CoV-2, Vaccine, Vaccine development, Immunity, antibody, SARS-COV-2 infection, susceptibility, disease severity, systematic review, heterogeneity, RNA, Adults, Epitopes, Asymptomatic, Surveillance, Research, understanding, epidemiological, disease, Critical, T cell response, Critical disease, cross-reactive, Consensus, Inference, recipients, paper, COVID-19 case, complex, population level, pauci-symptomatic, article, finding, T cell memory, T cell lymphopenia, researcher, uninfected, limitations, responses, robust, researchers, Result, lack, develop, evaluate, carried, involved, unlikely, screened, majority, demonstrated, hospitalised patient, feasible, individuals, virus-specific T cell, peer-reviewed, methodological limitation, preserved, synthesised, 【제목키워드】 SARS-COV-2 infection, systematic review, T cell response,