The proposed study is a single center, randomized and controlled human study to optimize controlled human malaria infection (CHMI) administered by direct venous inoculation (DVI). 30 to 36 participants will be randomized to one of five groups and will be inoculated with PfSPZ Challenge DVI. All participants recruited will be healthy adults aged between 18 and 45 years. The study duration is 4 months, participation duration is estimated to be 2 months. Safety and infectivity data will be collected for each study product and dose-level. Sera will be collected at baseline and at study day 29 for antibody assays. Participants, and clinical and laboratory investigators will be blinded to group allocation. The study primary endpoint will be reached at study day 29, at which time an interim study report will be generated. The investigators, the sponsor, the data and statistical analysis team, and Sanaria staff will meet in person or by teleconference on day 43 to review infection, pre-patent period, and adverse event results. These results will be made available to members of the International PfSPZ Consortium (I-PfSPZ-C) and if required, to regulatory authorities, including the FDA, to facilitate other PfSPZ Challenge CHMI studies with the appropriate disclaimers. Participants will be followed as outpatients for malaria diagnosis, treatment and follow-up to study day 57. Malaria positivity will be determined by qPCR diagnostics with microscopy as a backup. Participants who test positive for malaria and those who remain negative at study day 29 will be treated with oral atovaquone-proguanil. The primary objective of this study is to assess the safety and reactogenicity of PfSPZ Challenge administered by DVI using 7G8 and NF54 P. falciparum strains. Secondary objectives are to 1) assess the infectivity of four escalating doses of direct venous inoculation (DVI) of the 7G8 clone in comparison with an established dose (100% infective) DVI of the NF54 strain and 2) assess the time to malaria patency for escalating doses of the 7G8 clone compared to a single dose of the NF54 strain.