Researchers want to better understand Plasmodium vivax, one of the most common types of malaria parasites. The study will examine how the parasite grows in the blood, how the immune system responds to malaria, and how malaria can be transmitted from an infected person to mosquitoes.

No malaria vaccine is being tested in this study. However, what researchers learn may help scientists develop and test malaria vaccines in the future.

You may be eligible for this study if you meet the following criteria.

Inclusion Criteria:

• In good health
• Willing to stay overnight as an inpatient for 3-5 days
• Willing to live with another person during the study
• Ages 18-54
• Not currently pregnant or breastfeeding, or planning on becoming pregnant or breastfeed until the end of study
• Not diagnosed with HIV, hepatitis B, and/or hepatitis C
• Willing to use reliable contraception
• Reliable access to the NIH clinical center in Bethesda, MD for the duration of the study
• No history of a severe reaction to insect bites, or history of anaphylaxis or severe unexpected allergy to any substance
• Not smoking more than 5 cigarettes or equivalent per day
• Willing to be infected with malaria under the supervision and care of the study team

Additional eligibility requirements apply. The study team will determine whether the study is appropriate for you during screening.

Your participation will last approximately 1 to 3 months.The period from receiving the malaria challenge injection through your final study visit is expected to last about 1 month. Screening and scheduling before the injection may take up to an additional 2 months. You will complete several outpatient appointments, receive phone calls from the study team, and stay overnight at the NIH Clinical Center for approximately 3–5 days.

Step 1: Screening

Before joining the study, you will complete screening to determine whether the study is a good fit for you. Screening begins with a phone interview. If you appear eligible, you will be asked to complete an in-person screening visit at the NIH Clinical Center. The screening visit may include health assessments and testing to make sure it is safe for you to participate. You will receive $200 for completing the screening visit.

Step 2: Malaria Challenge

If you qualify and choose to participate, researchers will intentionally infect you with P. vivax malaria using a malaria challenge agent. You are expected to develop malaria symptoms approximately 1–2 weeks later. Symptoms may feel similar to having the flu. The research team will closely monitor you through clinic visits and phone calls during this period.

Step 3: Inpatient Hospital Stay

Once you develop specific symptoms or meet the study’s criteria for admission, you will be admitted to the NIH Clinical Center. You should expect to stay in the hospital for approximately 3–5 days, although the exact length of your stay may vary. During your stay, the research team will closely monitor your health and malaria infection.

Step 4: Mosquito Feeding Procedures

Researchers also want to learn whether malaria can be transmitted from an infected person to mosquitoes. During your inpatient stay, you will participate in mosquito feeding procedures. For each procedure, researchers will place 1–2 cups containing mosquitoes against the skin of your arms for about 15 minutes, allowing the mosquitoes to bite. These procedures may occur multiple times during the study. Researchers will later study the mosquitoes to determine whether they became infected with the malaria parasite.

Step 5: Malaria Treatment

During your inpatient stay, you will receive medication to treat and cure your malaria infection. The research team will continue monitoring you to make sure the treatment is working and that the infection has cleared.

Step 6: Follow-Up

After leaving the hospital, you will continue to have follow-up clinic appointments and phone check-ins. Researchers will monitor your health and confirm that you have fully recovered and that the malaria infection has been cured.

You will receive $200 for completing the screening visit.

If you enroll and complete the study, you may receive approximately $4,025 in total compensation. Your exact compensation may vary depending on when you are admitted to the NIH Clinical Center, how long you remain an inpatient, and which study visits you complete.

Participants are paid for each qualifying study appointment they complete.

There is no cost for you to participate in our research study.