Figure 2.

Intervention effect on parasite population. This schematic represents the potential impact of different interventions (e.g., bednets, vaccines, or drugs) on allele frequencies in the parasite population. The different colored circles represent a specific locus of interest such as an allele or haplotype that may be subject to selection by a vaccine (green circle) or drug (red circle). As a vaccine (e.g., a monovalent protein subunit vaccine like RTS,S) is applied, there may be reduction in specific parasite types that harbor the target locus (e.g., the circumsporozoite [CS] locus that matches the type found in the vaccine), thus reducing parasite types with that specific locus from the parasite population. As a drug is applied, there may be selection for a specific drug resistance locus resulting in an increase in the frequency of parasite types that harbor that specific drug-resistant variant. For comparison, use of a bednet might reduce the overall parasite types (represented by fewer circles that are proportionally reduced), but may not specifically select for or against any particular locus or allele within parasites in that population.