Diseases and vaccines

Malaria

PATH is working to accelerate the development of promising malaria vaccines and ensure their availability and accessibility in the developing world. Learn more about PATH’s efforts in malaria vaccine development. PATH also works on malaria prevention and treatment in Africa, using mosquito nets, insecticide, and medication. Learn more about PATH’s efforts in malaria control. For further resources on malaria control in Africa, please visit the MACEPA Learning Community website.

Malaria disease

  • Among the four species of the malaria protozoan parasite, Plasmodium (P.) falciparum is the deadliest.
  • Every year, P. falciparum malaria causes the deaths of more than one million people, most of them sub-Saharan African infants and children. Malaria also contributes to anemia in children and pregnant women, low birth weight, premature birth, and neurological damage. An estimated 300 million to 500 million cases of malaria occur every year, and roughly 3.2 billion people are at risk of contracting the disease.
  • Malaria is transmitted by the female Anopheles mosquito, of which there are more than 40 species. Malaria transmission, which is affected by climate and geography, often coincides with the rainy season.
  • Malaria-control strategies include the use of medicines, insecticides, and insecticide-treated screens and bednets. Control programs led to the elimination of malaria from Australia, Europe, and the United States by the 1950s.
  • Malaria can be treated with a regimen of antimalarial drugs based on the type of infection and status of the patient.

Malaria vaccines

  • No licensed vaccine against malaria currently exists.
  • The malaria vaccine community aims to license—by 2015—a first-generation vaccine that has 50 percent efficacy against severe disease and death, with protection lasting at least one year without the need for boosting. They also aim to license—by 2025—a second-generation malaria vaccine that has a protective efficacy of at least 80 percent against clinical disease and with protection lasting for many years without a booster.
  • Malaria vaccines in development include: pre-erythrocytic or liver-stage vaccines that aim to protect against the early stage of malaria infection; blood-stage vaccines that aim to reduce the severity of disease; and transmission-blocking vaccines that are intended to prevent mosquitoes that fed on an infected person from spreading malaria to new hosts.
  • The development of malaria vaccines is complex for several reasons:
    • The size and genetic complexity of the parasite mean that each infection presents thousands of antigens to the human immune system. Understanding which of these can be a useful target for vaccine development has been complicated, and to date at least 40 promising antigens have been identified.
    • The parasite changes through several life stages even while in the human host, presenting a different subset of molecules for the immune system to combat at each stage.
    • The parasite has evolved a series of strategies that allow it to confuse, hide, and misdirect the human immune system.
    • It is possible to have multiple malaria infections of different strains at the same time.

References