Figure 1

Trial profile. In Tübingen the IV dose of PfSPZ Challenge IV was increased sequentially in 4 steps from 50 (1), to 200 (2), to 800 (3) and to 3,200 PfSPZ (4). In steps 1 and 2, volunteers were randomly assigned to receive PfSPZ Challenge ID or IV. An independent verification group (3,200 PfSPZ DVI) in Barcelona was added after completion of the 3,200 PfSPZ IV group in Tübingen.