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The World Health Organization (WHO) recommended the use of RTS,S/AS01 malaria vaccine for the prevention of P. falciparum malaria in children residing in regions with moderate to high transmission rates. Recently, a second vaccine, R21/Matrix-MTM, was recommended by the WHO. Implementation of both R21 and RTS,S and R21 vaccines has the potential to significantly contribute to malaria control.
BACKGROUND
Malaria,
a persistant disease
Malaria remains a significant global health issue, with approximately 249 million cases and 608,000 fatalities reported in 2022. It primarily affects the most susceptible groups, children under the age of 5 which represented 78,1% of malaria-related deaths in the WHO African Region in 2022. Other regions with a notable presence of P. falciparum include parts of Southeast Asia and South America.
Current public health efforts and strategies to combat malaria involve a combination of preventive measures such as bed nets, early diagnosis, vaccines and antimalarial drugs. Among these strategies, vaccines emerge as the most promising tools for prevention.
Malaria vaccines
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P. falciparum life cycle. Modified from Bousema & Drakeley 2011 Clinical Microbiology Reviews
Malaria vaccines can target various stages of the parasite's life cycle. Vaccines targeting the pre-erythrocytic stage prevent liver infection, those focused on the erythrocytic stage control the presence of the parasite in the bloodstream, and transmission-blocking vaccines interfere with the spread from humans to mosquitoes, thereby reducing transmission. Multistage vaccines aim to offer comprehensive protection by addressing various parasite life cycle stages.
The World Health Organization (WHO) recommended the use of RTS,S/AS01 malaria vaccine for the prevention of P. falciparum malaria in children residing in regions with moderate to high transmission rates. Recently, a second vaccine, R21/Matrix-MTM, was recommended by the WHO. Implementation of both R21 and RTS,S and R21 vaccines has the potential to significantly contribute to malaria control.
Malaria: challenges on vaccine development
Despite years of dedicated efforts within the scientific community to develop malaria vaccines, there are still important challenges to tackle.
The key challenges involve the need for innovative vaccine approaches to amplify overall protective effects, a limited understanding of mechanisms related to liver adaptive protective immunity, and the complexity introduced by a lack of knowledge about protective antigens.
Additionally, extended timelines for pre-clinical and clinical testing of new malaria candidates further exacerbate the challenges.