A recent study carried out by researchers in Burkina Faso and the UK, and published in The Lancet Infectious Diseases, has shown that the first blood-stage malaria vaccine, RH5.1/Matrix-M, is safe, effective, and highly immunogenic. This double-blind, randomised, controlled, Phase IIb trial, which analysed 361 children between the ages of five months and 17 months, shows promise and highlights the potential for RH5.1/Matrix-M to be a component within a developing malaria vaccine strategy.
Malaria is a mosquito-borne disease, caused by parasitic Plasmodium protozoans, spread primarily through the bite of an infected female Anopheles mosquito. Symptoms can range from fever, chills, and headache, to confusion, seizures, and difficulty breathing.
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While progress has been made to certify nations as malaria-free, the burden of malaria remains high, particularly within the World Health Organization’s (WHO) African Region. According to the WHO, there were over 260 million cases of malaria and nearly 600,000 malaria deaths worldwide in 2023. Approximately 95% of these deaths occurred in the WHO African Region, where malaria cases continue to rise. Malaria is a leading cause of death for children under five years of age in the WHO African Region.
There are currently only two malaria vaccines that are WHO-prequalified and recommended for use in children, GSK’s Mosquirix and the Serum Institute of India’s R21/Matrix-M. The recommendations of Mosquirix and R21/Matrix-M by the WHO are relatively recent and occurred in 2021 and 2023, respectively. These vaccines are pre-erythrocytic, meaning they work to intercept malaria infection by targeting the early sporozoite stage of the parasite. However, as immunity wanes with time, sporozoites can infect the liver and lead to blood-stage clinical malaria infection. The development of a blood-stage malaria vaccine would not replace pre-erythrocytic vaccines, rather it could provide a second line of defence.
RH5.1/Matrix-M was found to be 55% effective against clinical malaria when administered in a delayed third-dose regimen at 0, one, and five months. Further, the vaccine demonstrated over 80% efficacy against high levels of malaria parasites, which indicates the vaccine would be effective at preventing severe disease. RH5.1/Matrix-M was found to be generally safe and well-tolerated, with no serious adverse events being reported. The most common adverse events were swelling at the injection site (3%) and fever (14%). These rates are favourable to those observed in the Phase III trials of Mosquirix and R21/Matrix-M, in which swelling was observed after 10% and 4% of vaccinations and fever was observed after 31% and 47% of vaccinations, respectively. According to leading data and analytics company GlobalData, there are 11 other malaria vaccines currently in Phase II development, including pre-erythrocytic vaccines and blood-stage vaccines from manufacturers such as BioNTech, GSK, the National Institute of Allergy and Infectious Diseases, and Vac4All SAS. No new malaria vaccines are in Phase III development or preregistration at this time.
RH5.1/Matrix-M has the potential to be the first blood-stage malaria vaccine brought to market. This could be a much-needed addition to the currently available malaria vaccines and provide an important second line of defence for those most at risk of contracting malaria.
