Balanced activation of acquired SARS-CoV-2 specific immune responses, which include CD4+ and CD8+ T cells with a memory phenotype and neutralizing antibody responses, is required for host protection in acute COVID-19 (Rydyznski Moderbacher 2020; Mudd and Remy 2021; Sette and Crotty 2021). Here, CD4 is linked to COVID-19.