Maybe on account of the long line of clinical trial failures, at present there appears to be a tilt towards whole organism vaccine. Even though it may be possible to generate large number of irradiated or genetically modified sporozoites, concerns regarding the safety of injecting humans with parasites that have been grown in human RBCs and mosquito cells will remain. There is always the possible risk of unidentified pathogens being delivered with the vaccine. Human erythrocytes are the primary source for clonal amplification of genetically modified parasites as of now. Circumventing this phase of growth does not appear to be possible in the near future.