CD4 and infection: In our study (Marlin et al., 2021), an extensive evaluation of the immunological response has been performed with quantification of spike-binding antibodies, antibodies inhibiting the attachment of RBD to ACE2, antibodies neutralizing infection, SARS-CoV-2-specific CD4+ and CD8+ T cells producing cytokines and serum cytokine levels (Figure 3, Figure 1—figure supplements 3–5).