It is intriguing to note that despite the presence of pre-existing anti-CSP antibodies and coupled with the fact that in the MVA-CSP/IL-15 vaccinated mice, the parasitic burden in the liver was markedly reduced, yet we failed to detect any delay in the patency of P. yoelii or any reduction in the magnitude of parasitemia in the early phase of infection in the MVA-CSP/IL-15 vaccinated mice. This evidence concerns the gene IL15 and parasitic infectious disease.