These assessments of the magnitude of the spike-specific T cell response together suggest that (1) in infection-naïve individuals the CD4+ T cell response is boosted by the second vaccination dose, (2) convalescent individuals exhibit a more disparate response, with most donors mounting a weaker response than infection-naïve individuals, and (3) the response is more robust among CD4+ than CD8+ T cells. This evidence concerns the gene CD4 and infection.