Current Status and Prospects of Malaria Vaccines

Malaria is a parasitic disease caused by four Plasmodium species infecting humans, Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. The parasite is transmitted by the Anopheles mosquitoes that flourish in warm climates. These vectors thus are present in many tourist areas of the world, including Africa, Asia, and South America. Known in China, as far back as 2700 BC, malaria was controlled by medicinal plants or drugs. This was until drug resistance occurred, beginning in Asia with chloroquine in the 1960s and spreading quickly all over the world. Today, the status of malaria drug resistance is critical and has lead to the appearance of virulent and deadly P. falciparum strains that are difficult to control. In addition, the number of cases of malaria has increased owing in part to an increase in the spread of malaria caused by another flying vector: the airplane. Airplanes can carry not only infected travelers, but also, sometimes, mosquitoes. As an example, more that 1000 cases of imported malaria were reported in 1992 in the United States, where malaria had previously been eradicated. The mosquito vector (personal communication, Centers for Disease Control, Atlanta, GA) still exists in the U.S., and recent acquisitions of malaria among persons living in New Jersey and Texas, who had no risk factors for malaria, underscores the potential for imported malaria to affect the nonimmune host population in any country in the world.