CD4 and COVID-19: Our findings contrast this observation, with all CVID seroresponder and 5/6 non-seroresponder showing a robust polyfunctional CD4+ T cell immune response thus complementing previous reports of robust specific SARS-CoV-2 T cell responses in CVID patients with mild [28] and severe SARS-CoV-2 infections [29] as well as to COVID-19 vaccination [8–10] and other vaccines, such as influenza [30, 31].