E. John Wherry III PhD is an immunologist and the Richard and Barbara Schiffrin President’s Distinguished Professor and department chair of Systems Pharmacology and Translational Therapeutics at the University of Pennsylvania. He is also the director of the Penn Institute for Immunology. For decades John has studied T cell activity in the context of chronic viral infection, for example his lab delineates mechanisms by which chronic viral infection can lead to T cell exhaustion. Lately John’s laboratory has been studying how T cells respond to the SARS-CoV-2 virus and vaccines that contain the SARS-CoV-2 spike protein. He is now moving his research into LongCovid, where he is working to determine if the activity of T cells can be used as biosensors of SARS-CoV-2 persistence in patients with the condition.