CD4 and malaria: Most recently, we have demonstrated the safety and immunogenicity of a heterologous prime-boost approach using a chimpanzee adenovirus (ChAd63) and modified vaccinia virus Ankara (MVA), both encoding the ME-TRAP subunit.29, 30, 31 This regimen induces cellular immunity comprising both CD4+ and CD8+ phenotypes and IgG antibody responses in malaria-naive and semi-immune adults.32, 33 Against CHMI with P. falciparum-infected mosquitoes, ChAd63 MVA ME-TRAP elicited 21% sterile efficacy and significantly delayed the time-to-patency of malaria in a further 36% of vaccinees.34