Parasite growth inhibition activity of protected and non-protected monkeys. A) Post vaccination B) post challenge. Mean GIA inhibition levels of total IgG isolated from monkey serum from animals in control (mock) group, CSP/SSP2 group, and Pk4x3/COPAK vaccinated animals (protected or not protected animals are shown). Final IgG concentration added to P. knowlesi parasite culture was 6 mg/mL. Geometric shapes represent individual animals in each group, throughout all figures. For one animal in the control group no post challenge data are available, as it died for study-unrelated reasons.