Figure 2.

Net OD 1.0 IgG antibodies to PfCSP by ELISA 14 days after the third immunization with PfSPZ Vaccine or normal saline, by group. Horizontal arms represent medians and are bracketed by the interquartile range. Each point represents the results for a unique participant. Filled circles (⬤) represent participants not infected after CHMI; open circles (○) represent participants who were infected after CHMI (ages 18–35 years only).¹⁴ Crossed circles (⊗) represent participants who did not undergo CHMI, and open triangles (Δ) represent participants who received placebo. Net OD antibody levels were significantly different between vaccinees and placebo recipients in 18–35-year-olds (P < 0.001), 11–17-year-olds (P = 0.002), and 6–10-year-olds (P = 0.002) but not 36–61-year-olds (P = 0.11, Mann-Whitney two-sided test). No sera were available from controls in the 1–5-year-old and 6–11-month-old age groups. CHMI = controlled human malaria infection; PfCSP = Plasmodium falciparum (Pf) circumsporozoite protein; PfSPZ = Plasmodium falciparum sporozoites.