Figure 3

Variable sensitivity can obscure differences between vaccinated and unvaccinated individuals in challenge studies. If blood smears are read by two different microscopists at time = t₁ and time = t₂, differences in sensitivity could result in no difference seen between the two study subjects. Microscopist A with an LOD of 50 p/μl would read negative smears at time t₁. Microscopist B with an LOD of 10 p/μl would read positive smears at time t₂. An initial number of merozoites are released from the liver at time t = 0 and assumed to grow exponentially with 16 merozoites produced from a single merozoite every 48 hours. The table inset gives the "window of detection" of blood-stage infection when the sensitivity varies between 10 and 100 parasites per microliter for different numbers of primary merozoites released from the liver.