CD4 and viral infectious disease: Furthermore, mechanistic studies in animal models, such as the demonstration of a substantial reduction in the ability of antibodies to control the viral infection in CD8 T cell-depleted SARS-CoV-2 convalescent [28] or vaccinated [29] macaques or the ability of CD4 T cells to reduce lung pathologies in a mouse model of SARS-CoV-2 [30] clearly showed the importance of SARS-CoV-2 T cells in protecting from the pathological consequences of infection.