CD4 and COVID-19: On the basis of these emerging COVID-19 translational immunogenicity data, in addition to being safe, an optimal SARS-CoV-2 vaccine should (i) induce robust and durable CD8+ and CD4+ T cell responses, (ii) elicit high-magnitude neutralizing antibodies, (iii) produce TH1 bias in the elicited antibody and T cell responses, (iv) potentially expand preexisting cross-reactive T cells, (v) enable dose sparing of required immunogens to improve the speed and cost of broad vaccination campaigns, and (vi) be efficacious in elderly populations.