Background: People get malaria from bites from infected mosquitos. Researchers are studying a vaccine strategy. They will give people malaria parasites by injecting them with live infectious malaria parasites with antimalarial medications and then see if this strategy prevents malaria infection while off antimalarial medications. Objective: To see if combining a high dose of live, infectious malaria parasites (known as Sanaria PfSPZ Challenge) and two FDA approved drugs that kill malaria parasites (pyrimethamine \[PYR\] OR chloroquine \[CQ\]) is safe and can provide people protection against malaria. Eligibility: Healthy adults ages 18-50 who: * are not pregnant or breastfeeding or planning on becoming pregnant while in the study * are not infected with HIV, Hepatitis B or Hepatitis C * have reliable early morning access to the NIH Clinical Center * are able to come to the outpatient clinic frequently, sometimes daily * have not been diagnosed with malaria within the past 10 years Design: * Participants will be screened with medical history and physical exam. They will have heart, blood, and urine tests. * Participants will have blood drawn for tests at most visits. * Participants will keep track of their temperature and symptoms during some sections of the study. * Participants will join one part of the study. Part 1 is one month: * Participants will get the parasites by an injection into a vein on day 1 and receive antimalarial medications. * They will have daily visits on days 7-14 * They will take another antimalarial at visits on days 15-17. * The final visit will be on day 29. Part 2 is seven months: * For the first 3 months, participants will get the parasite injection into a vein for 3 injections in total. Each injection will occur once per month while taking an antimalarial drug. * They will have daily visits on days 7-14 after the first injection, and on days 7-11 after the second and third injection. * They will have a final (fourth) injection around month 6 without any antimalarial medication. * After this fourth injection, participants may have up to 21 daily visits from day 7 after injection until end of study. Part 3 is one month: * Participants will get the parasites by injection into a vein on day 1 without antimalarial medications. * They will have visits almost every day starting day 7 from injection. * They will take an antimalarial medication when they are diagnosed with malaria * They will return for final end of study visit on days 27-29.
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AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.
Number of Participants With P.Falciparum Blood Stage Infection
Timeframe: 14 days post PfSPZ Challenge injection
Number of Participants Requiring Treatment With Additional Anti-malarial Medication
Timeframe: 12 days post PfSPZ Challenge injection
Number of Participants With Local and Systemic Adverse Events (AEs)
Timeframe: 7 months
Number of Participants With Serious Adverse Events (SAEs)
Timeframe: 7 months