To assess the safety and tolerability of NMRC-M3V-Ad-PfCA, in a dose-escalation design (Part A), in healthy malaria-naïve adults. Part A was a dose escalation of NMRC-M3V-AdPfCA (2 antigen combination) using two dose groups, 2x10\^10 pu (Group 1) and 1x10\^11 pu (Group 2). Subjects received a single intramuscular injection with the injections in the 2 groups staggered by 4 weeks in order to assess the safety and tolerability of the vaccine and define the dose to be used in Part B. The vaccine was to be considered safe and well-tolerated if there were no severe or serious adverse events related to vaccine administration.

To assess the safety and tolerability of NMRC-M3V-Ad-PfCA, in a regimen-comparison design (Part B), in healthy malaria-naïve adults. Subjects in part B received 2 intramuscular injections given 16 weeks apart: Group 3 NMRC-M3V-Ad-PfCA (2 antigen combination) at a dose of 2x10\^10 pu, or Group 4 NMRC-MV-Ad-PfC (single antigen) at 1x10\^10 pu dose. The vaccine was to be considered safe and well-tolerated if there were no severe or serious adverse events related to vaccine administration.

Protective efficacy was assessed by conducting a homologous 3D7 strain sporozoite challenge 3 weeks after the second NMRCMV-Ad-PfC immunization. Time to parasitemia was measured in both vaccinated and unvaccinated volunteers (infectivity controls) in Group 3 (NMRC-M3V-Ad-PfCA (2 antigen combination) at a dose of 2x10\^10 pu) and Group 4 (NMRC-MV-Ad-PfC (single antigen) at 1x10\^10 pu dose). Infectivity control subjects were challenged with Group 3 and Group 4. Each volunteer was monitored for the onset of signs and symptoms of malaria and by daily Giemsa-stained thick blood films with positive films confirmed by a second reader. The identity of immunized and non-immunized volunteers was known to the clinical trial staff but not to the microscopists reading the malaria smears.