Fig. 1

Flow chart. Eighty-nine candidates were tested for eligibility and fourty-six were included in the study after screening: twenty-three in cohort A (three additional participants started mefloquine prophylaxis in case of dropouts prior to the first immunization), twenty in cohort B, and three in the control groups. Participants in cohort A were randomized to receive immunizations with either three times fifteen NF135-infected mosquitoes (high-dose) or three times five NF135-infected mosquitoes (low-dose). One participant dropped out after the first immunization and two participants after the third immunization, all three because of personal or logistical reasons. Participants in cohort B received one immunization with fifteen NF135-infected mosquitoes (high-dose). The control group was not immunized. Immunized participants from cohort A, and three malaria-naïve control participants were challenged by bites of five NF135-infected mosquitoes. In cohort B, the trial was prematurely ended after the first immunization and participants were not subsequently challenged