CD4 and infection: The second major outcome of our study is that it highlights diversity in the quality of T-cell responses: between vaccines and between the CD4+ and CD8 + T-cell compartments; given the wider importance of T-cell quality beyond magnitude being important in antiviral immunity26,27, our data calls for further studies to understand the functional nature of SARS-CoV-2 -specific T-cell immune responses and their persistence in the context of both infection and vaccination.