Minimal efficacy requirements for malarial vaccines to significantly lower transmission in epidemic or seasonal malaria.

The effect of vaccines against the pre-erythrocytic, the erythrocytic and the sexual stages of malaria on the transmission of malaria was examined using a simulation model of seasonal or epidemic transmission. The primary outcome of the model was the number of cases of malaria present at the end of the transmission season. A range of efficacy for the vaccine, or of coverage of the population and of vectorial capacities were tested for each vaccine type. For a similar level of efficacy or coverage under conditions simulating hypo or mesoendemic malaria, all types of vaccines gave similar decreases in the number of people infected. Although all vaccine types gave significant reductions in malaria incidence at efficacy or coverage levels considerably lower than that required to completely block transmission, this reduction in case numbers was highly dependent on the vectorial capacity. The simulation model is equally applicable to other transmission blocking measures such as insecticide treated bed nets.