CD4 and infection: Experimental studies using P. chabaudi chabaudi AS (Pcc) infection, a murine model of chronic infection, demonstrated that persistent infection can maintain effector and memory CD4+ T cells, which effectively control re‐infection, and that the loss of protective immunity against blood‐stage infection correlate with the progressive decline in memory T cell responses (Achtman et al, 2007; Freitas do Rosario et al, 2008; Opata et al, 2018).