Expired Study
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Clinical Trial 8318

Silver Spring, MD 20910

Study Summary:

This study is researching malaria vaccines. Malaria is a disease that can range from mild illness to death. Humans get this disease by being bitten by mosquitoes that are infected with malaria parasites. While not found in America, it is in places such as Africa, Asia and Latin America. There are 300 – 500 million clinical cases and 1-2 million deaths annually. Ways to prevent getting sick with malaria include avoiding mosquitoes (using screens on windows, using bed nets or wearing insect repellant) or taking medicine once a day or once a week in order not to become sick. But a vaccine to protect against malaria, much like a flu vaccine protects against flu, would be beneficial both to people living in, or traveling to, areas where it is commonly found.

In the life cycle of the malaria parasite, a mosquito, carrying the malaria organism, bites a human and injects the parasite into the skin. Then the parasite moves to the liver, where it multiplies greatly. The person does not know he/she is carrying the malaria parasite at that time. Then after about 7-10 days, the malaria parasite enters the bloodstream and starts to invade red blood cells and multiply within the body. This is when the human feels very sick. He/she can develop flu-like symptoms at first (fever, body aches, headache, chills, sweats, fatigue etc) but then if the infection is not treated, many red blood cells can be destroyed causing anemia, and all body systems can start to malfunction (like liver and kidney failure), eventually leading to coma, and even death. When the parasite is circulating in the blood, a scientist can take a sample of blood and looking under the microscope, see the malaria parasite. This is how we diagnose malaria. Then anti-malaria medications can be given to cure the disease.

Vaccine Information: The experimental vaccine is called GAP- which stands for genetically attenuated parasite. What this means is that researchers have taken the malaria parasite and changed it so that it cannot fully develop. So when you give the GAP vaccine to a person, the body thinks it is “seeing” malaria and thus develops an immune response against it. Since the malaria parasite has been altered, it doesn’t go on to cause disease. Then if the person were to travel to an area and get “real” malaria, the body would already have defenses against it. This type of vaccine is the same type of vaccine used for measles or chicken pox and the nasal flu vaccine.

Since we are giving the whole malaria parasite as a vaccine, we would like to give it the same way it is given in nature - by mosquito bite. Someday, we will be able to give it by injection or another method, but at this time, we are testing it with mosquitoes.

In the secure insectary at WRAIR, we have mosquitoes that have never been out of the insectary. We can have these mosquitoes take up the GAP (the altered malaria organism). Then we will have the GAP-infected mosquito bite you. This will inject the GAP product in- much like regular vaccine. The GAP can go from the skin to the liver but because it is has be altered by researchers, it cannot grow and multiply in the liver. That means that the malaria organism will not develop to enter the bloodstream- and no clinical signs/symptoms of malaria will develop.

The vaccine is not licensed by the FDA; which means it is experimental and has FDA approval to undergo testing like in this study. The vaccine has been made under conditions acceptable to the FDA. This vaccine has been tested in mice and has been found to be safe.

Giving a malaria vaccine by mosquito bite has been done before at WRAIR. In these instances, the malaria parasite was put into mosquitoes and then put underneath x-rays. (The x-rays changed the parasite so it could not fully develop in humans.) The mosquitoes bit the human volunteers and thus transferred the altered malaria parasite to volunteers. Later, the volunteers were given malaria. A very large percentage of theses volunteers were protected- meaning they never got sick. We believe their immune system recognized and eliminated the wild type malaria because they had seen an altered form of malaria previously. Several studies like this one showed that volunteers needed to be bit by at least 1000 x-rayed mosquitoes be protected. We will also aim to have 1000 bites. To get to this number of bites, we are aiming to have 200 bites per session with a total of six sessions. We may find we need more if after 6 sessions we don’t get > 1000 bites. We will be showing you a short video on how the bites are given.

Goals of the Study: To see if a new investigational malaria vaccine is safe, how study volunteers immune system reacts to the vaccine and whether the vaccine can prevent or postpone malaria.


  • Men and non-pregnant, non-lactating women
  • ages 18-55 (inclusive)
  • in good health
  • no plans to travel to a country with malaria throughout the study
  • low cardiac risk
  • History of malaria or receipt of an investigational malaria vaccine
  • Recent travel to P. vivax endemic area within the past three months
  • Heart, lung, liver, or kidney disease (high blood pressure, diabetes)
  • Neurologic disease
  • Splenectomy
  • History of sickle cell disease or other blood diseases
  • Positive for HIV or hepatitis C
  • Use of investigational drug or non-registered vaccine within 30 days before the first immunization
  • Use of any licensed vaccine within 7 days before the first immunization
  • Allergic reaction to a vaccine
  • Pregnancy or planned pregnancy during the study time period
  • Use of certain prescription medications
  • Inability to make all follow-up appointments
  • Alcohol or drug abuse

Qualified Participants May Receive:

Compensation and free medical screening

Clinical trials are medical research studies designed to test the safety and/or effectiveness of new investigational drugs, devices, or treatments in humans. These studies are conducted worldwide for a range of conditions and illnesses. Learn more about clinical research and participating in a study at About Clinical Trials.