According to "Current Science" magazine, "some scientists estimate that malaria has killed half the people who have ever lived."  Today in Africa, malaria kills 3 children every minute and between 1 and 3 million people every year. 

Attempts to develop a vaccine have been hindered by the complex nature and adaptability of the parasite.  But a vaccine may finally be on the way. Melinda Smith narrates.

Nancy waits patiently to be bitten by malaria-carrying mosquitoes.  She is a volunteer in the research for a vaccine against malaria.

The search for a vaccine is one of the most complex and extensive challenges for the scientific community around the world, and it's been a real struggle.  Here at the Walter Reed Army Institute of Research in Washington DC, the first vaccine against malaria was tested in 1985, with little success.  There have been improvements since then, but the chief physician of the Malaria Vaccine Program, Colonel Gray Heppner, says it is difficult to completely prevent a disease carried by a parasite.

"There has never been a vaccine against an organism this complex; there has never been a successful human vaccine against a parasitic disease," says Dr. Heppner.

At the moment, two possible vaccines,called RTS-S and MSP-1, are being tested at Walter Reed and in Africa.

"The vaccine we are working on has two major strategies: the first is to prevent malaria in the first place and the second is to limit the disease severity," says Dr. Heppner.

A team lead by scientists Jeff Lyon and Evelina Angov have been working on prevention for 10 years. They have developed a protein that looks like the parasite, which can train the human immune system to protect itself against malaria.

"We think that this protein may mimic more of the native structure in the parasite," says Dr. Angov.

Testing the vaccines is dangerous work. In a hot and very humid environment, Dr. Jack Williams raises thousands of mosquitoes.  He is in charge of the insectaries and the Malaria Transmission laboratory.

"We give these mosquitoes a blood meal twice a week.  This probably contains close to 7,000 or 8,000 mosquitoes," says Dr. Williams.

The mosquitoes must be infected to make sure they are carrying the malaria parasite. The work takes place behind 7 sets of doors, with intense safety measures.

Dr. Williams says, ?each of those cartons contains 300 to 400 malaria-infected mosquitoes." Once the mosquitoes have bitten a volunteer, technician Megan Dowler makes sure they had a meal of human blood; in other words, the parasite has a chance to pass from the mosquito into a human's blood stream.

Mosquitoes that feed would have bright red bellies. She then takes the now-fat mosquitoes to her lab, dissects them, and verifies that the malaria parasite was present.

Dr. Kent Kester, Chief of Clinical trials talks about how the vaccine is categorized and maintained, "In this refrigerator we store our investigational vaccines. They are segregated by study. For instance, this is investigational malaria vaccine."

Dr. Kent Kester has been involved in vaccine development since the early 1990s and has seen more than 20 different formulations of the vaccine.

As the chief of clinical trials, he has exposed more than 500 people to real malaria in the past 15 years. He himself was a volunteer in one trial and became infected with malaria. But now he sees real hope. "I think it is very promising. In fact, it is the most promising product we've had for a long time."

So far the vaccines aren't perfect. They don't work very long in the body -- just a few months. And they are expensive to develop, which slows the pace of research. Dr. Heppner says that additional malaria proteins are being tested and developed separately.

If they work, they could be put together with the RTS-S vaccine to create effective protection. "The present version doesn't meet the military requirement of protection for a long period of time. But it is quite possible that this vaccine developed as is or similar [may be sufficient] for public health. Remember, every minute three children die from this disease," he said.

According to Dr. Heppner, within the next 10 years we could have a licensed malaria vaccine. GlaxoSmithKline Pharmaceuticals, the Malaria Vaccine Initiative and USAID have funded the research for years, but manufacturing and distribution could cost several million dollars more and the international community will have to step in. Initial studies estimate that if the resources are there, 70 million people could be vaccinated by the year 2025.