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Malaria

Every year, malaria kills hundreds of thousands of people, most of them young African children. Malaria can be controlled through the use of medicines, insecticides, and insecticide-treated screens and bednets, and can be treated with antimalarial drugs. Currently, there is no licensed vaccine against malaria; however, several vaccines are under development.

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Malaria disease

  • Among the various species of the malaria protozoan parasite, Plasmodium falciparum is the deadliest.
  • Every year, P. falciparum malaria causes the deaths of hundreds of thousands of people, most of them sub-Saharan children younger than five years of age. Malaria also contributes to anemia in children and pregnant women, low birth weight, premature birth, and neurological damage. Hundreds of millions of cases of malaria occur every year.
  • 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 bed nets. 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—or against any parasite—has ever been available for widespread human use. In January 2016, the World Health Organization (WHO) recommended pilot implementation of GlaxoSmithKline’s RTS,S malaria vaccine candidate, also known as Mosquirix™. This recommendation confirmed the advice provided by two independent expert groups on vaccines and malaria—the WHO Strategic Advisory Group of Experts on Immunization and the Malaria Policy Advisory Committee.
  • RTS,S is also the first malaria vaccine candidate to have received a positive scientific opinion from a stringent regulatory authority. In July 2015, the European Medicines Agency issued a positive scientific opinion for RTS,S through its Committee for Medicinal Products for Human Use (CHMP). The CHMP provides scientific opinions, in cooperation with the WHO, on medicinal products that are intended exclusively for markets outside of Europe.
  • RTS,S is meant to complement routine methods that countries currently use to control malaria. The vaccine was developed to help prevent Plasmodium falciparum malaria among children in sub-Saharan Africa.
  • A multi-country Phase 3 efficacy trial demonstrated that RTS,S protected children over three to four years. Over the first 18 months following three doses of RTS,S, malaria cases were reduced by almost half in children aged 5 to 17 months at the time of first vaccination. At study end, four doses of RTS,S reduced malaria cases by 39 percent over four years of follow-up in children.
  • The pilots will enable first-time use of RTS,S in real-life situations to help determine the vaccine's potential role alongside other tools to prevent malaria. Specifically, they will assess the feasibility of providing four doses of RTS,S in routine health care services and gather additional data on safety and on the impact of the vaccine on child deaths.
  • The global malaria vaccine community is also building on current knowledge to develop the next generation of vaccines. According to the community's Malaria Vaccine Technology Roadmap, next-generation vaccines should show at least 75 percent efficacy against clinical malaria, be suitable for use in all malaria-endemic areas, and be licensed by 2030.
  • 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

Page last updated: February 2017.

Photo: PATH/Amy MacIver.