Interleukin 7 (IL-7) is a pleiotropic cytokine essential for lymphocyte survival and expansion.4,5 Administration of IL-7 invariably increases circulating and tissue lymphocytes and has been administered to more than 450 patients with an excellent safety profile.4,5 IL-7 is currently in multiple randomized clinical trials for oncologic and infectious disorders, and a trial in the United Kingdom is evaluating its use among patients with severe COVID-19. This evidence concerns the gene IL7 and infectious disease.