Malaria vaccine
The malaria vaccine is designed to induce immunity against the Plasmodium parasite, which causes malaria, a disease primarily transmitted by Anopheles mosquitoes. In 2022, approximately 249 million cases of malaria were reported globally, leading to around 608,000 deaths, particularly in sub-Saharan Africa where the majority of severe cases occur. The most critical species causing malaria are P. falciparum and P. vivax, among others. Vaccine development has become a priority, with significant research dating back to the 1990s. The RTS,S vaccine, also known as Mosquirix, showed partial efficacy in reducing malaria incidence but also decreased overall mortality in children under two. In late 2023, the R21/Matrix-M vaccine was approved by the World Health Organization, demonstrating even higher efficacy rates. While these vaccines have been integrated into routine immunization programs in several African countries starting in 2024, challenges such as production, equitable access, and vaccine hesitancy still exist. Experts emphasize that while vaccines are crucial, they should be part of a comprehensive strategy including preventive measures like treated nets and pesticides to effectively combat malaria.
On this Page
Subject Terms
Malaria vaccine
Definition
The malaria vaccine is a preparation designed to provide immunity against infection by the parasite Plasmodium, which leads to malaria.
Background
Malaria is caused by five species of Plasmodium.P. falciparum, P. vivax, P. malariae, and P. ovale cause about 90 percent of malaria cases and are responsible for the most deaths, particularly in Africa. P. knowlesi can also infect humans. The World Health Organization estimated in 2022 that 3.2 billion people were at risk for malaria exposure. About 249 million people contracted malaria worldwide in 2022, and an estimated 608,000 people died from the disease.
Plasmodia are transmitted by the Anophelesmosquito; the incubation period lasts between seven and thirty days, depending on the Plasmodium species transmitted. Symptoms of malaria include shivering, fever, headache, vomiting, and sweating. Severe malaria can involve such symptoms as impaired consciousness, seizures, coma, anemia, pulmonary edema, and cardiovascular collapse.
Vaccine Status
Preventing malaria infection is a top priority for many health and research organizations around the world, as they are trying to establish vaccines to protect against the disease. Research and development began in the 1990s. Many researchers have focused on developing vaccines against P. falciparum, while a few groups worked on a vaccine for P. vivax. The life cycle of P. falciparum is quite complex, as it provides several stages on which to focus vaccine development.
Numerous clinical trials have attempted to select safe, effective vaccines. Because of the complexity of the parasite’s life cycle, it is likely that multiple types of vaccines will be necessary to interrupt that life cycle.
Among the most advanced vaccine is RTS,S, or Mosquirix, which was studied in phase 3 trials in several countries in sub-Saharan Africa beginning 2009. The phase 2 trial for this drug showed 30 to 50 percent efficacy in reducing malaria in infants and children. Based on these results, it appeared that the vaccine would only partially protect those immunized. However, RTS,S also reduced all-cause mortality in children under two by 13 percent, likely meaning that it reduced their susceptibility to other potentially fatal conditions, such as bacterial infections and malnutrition. Due to the vaccine’s success, RTS,S was the only vaccine recommended by the WHO as an additional tool in the prevention of malaria in 2021.
Another promising vaccine is R21/Matrix-M, which joined the RTS,S vaccine in receiving WHO approval in late 2023. The latter vaccine achieved a higher level of efficacy than its predecessor, reaching up to 75 percent reduction.
Nearly thirty African countries added at least one of those vaccines in their routine immunization programs beginning in 2024. In January 2024, Cameroon became the first country to roll out the RTS,S vaccine to infants and young children, and R21 was set to roll out beginning in mid-2024. Production, distribution, and equitable access remained challenges, however. Vaccine hesitancy, especially over low efficacy, posed another difficulty among some Cameroonians.
Impact
A viable, disease-preventing malaria vaccine has the potential to save millions of lives by providing protection against Plasmodium infection. However, disease experts cautioned that even with effective vaccines, additional longstanding precautions to prevent disease spread, such as the use of treated nets and indoor application of pesticides, would continue to be necessary; used together, those tools could eliminate as much as 90 percent of cases.
Bibliography
Akua, Nalova. “A Turning Point: Cameroon Rolls out World’s First Malaria Vaccine.” VaccinesWork, Gavi, 22 Jan. 2024, www.gavi.org/vaccineswork/turning-point-cameroon-rolls-out-worlds-first-malaria-vaccine. Accessed 26 Feb. 2024.
Bajaj, Simar. “The Malaria Vaccine That Just Rolled Out Has a Surprise Benefit for Kids.” Goats and Soda, NPR, 24 Jan. 2024, www.npr.org/sections/goatsandsoda/2024/01/24/1226387171/the-malaria-vaccine-that-just-rolled-out-has-a-surprise-benefit-for-kids. Accessed 26 Feb. 2024.
Crompton, Peter D., et al. “Advances and Challenges in Malaria Vaccine Development.” Journal of Clinical Investigation, vol. 120, 2010, pp. 4168–78.
Enayati, A., and J. Hemingway. “Malaria Management: Past, Present, and Future.” Annual Review of Entomology, vol. 55, 2010, pp. 569–91. doi:10.1146/annurev-ento-112408-085423.
Johnson, Sarah. “Cheaper, More Effective Malaria Vaccine Wins WHO Approval.” The Guardian, 2 Oct. 2023, www.theguardian.com/global-development/2023/oct/02/new-malaria-vaccine-approved-by-world-health-organization. Accessed 26 Feb. 2024.
Mahamadou, A. Thera, et al. “Safety and Immunogenicity of an AMA1 Malaria Vaccine in Malian Children.” PLoS, vol. 5, 2010, p. e9041.
“Malaria.” World Health Organization (WHO), 4 Dec. 2023, www.who.int/news-room/fact-sheets/detail/malaria. Accessed 26 Feb. 2024.
“RTS,S/AS01.” PATH's Malaria Vaccine Initiative, www.malariavaccine.org/malaria-and-vaccines/rtss. Accessed 1 Mar. 2023.
Sherman, Irwin W. The Elusive Malaria Vaccine: Miracle or Mirage? ASM Press, 2009.
“10 Facts on Malaria.” World Health Organization, Nov. 2015, www.who.int/features/factfiles/malaria/en. Accessed 16 Nov. 2016.