A randomized, open-label clinical trial was designed to standardize a P. vivax sporozoite challenge model in malaria-naïve volunteers, specifically, the relationship between the number of infectious mosquito bites and the likelihood of developing patent parasitemia detectable by Giemsa-stained thick blood smear (TBS). The study was divided into two steps. Step A was designed to produce mature P. vivax sporozoites suitable for inoculation into humans; and Step B was designed to assess the safety and reproducibility of the sporozoite challenge. For Step A, patients with infective P. vivax gametocytes detected by TBS were recruited from the outpatient clinics at the Immunology Institute (IDIV) in Cali and Buenaventura, Colombia. Patients donated 35 mL of whole blood, which was screened for co-infections that could potentially represent a threat to the health of volunteers. The blood was then artificially fed to Anopheles mosquitoes.14 For Step B, malaria-naive subjects were exposed to the bites of 3 ± 1, 6 ± 1, or 9 ± 1 infected mosquitoes to determine the prepatent period of the infection and its reproducibility.