A first vaccine victim of its success, a second close to entering the scene: 2023 is a decisive year for the fight against malaria. While after twenty years of progress, this has been marking time since 2020, the deployment of the RTS,S (or Mosquirix) serum, from the British giant GSK, and the arrival of R21/Matrix-M, developed by the University of Oxford and recommended Monday October 2 by the World Health Organization (WHO), promise to take it a major step forward. By 2030, the WHO and the Global Vaccine Alliance (GAVI) anticipate requests of up to 100 million doses, the two institutions indicate in a joint press release.
“These two vaccines break the chain of transmission by blocking the action of the parasite before it passes the hepatic barrier (the liver), where it reproduces before passing into the blood. In this way, they are a valuable tool,” explains Didier Ménard, professor of parasitology at the University of Strasbourg and member of the “malaria genetics and resistance” unit at the Pasteur Institute in Paris.
After the success of the pilot phase carried out since 2019 in Ghana, Malawi and Kenya, which enabled 1.7 million children to receive at least one dose, demand for the Mosquirix vaccine had already exploded: 30 African countries have requested to benefit from its large-scale deployment, but only twelve of them were satisfied. Benin, Burkina Faso, Burundi, Cameroon, the Democratic Republic of Congo (DRC), Liberia, Niger, Sierra Leone and Uganda will join the first three beneficiary states and share the 18 million of doses produced for the period 2023-2025. “This request is unprecedented,” said Tedros Adhanom Ghebreyesus, WHO director-general.
A vaccinopole project in Senegal
The second vaccine should help bridge this gap and provide relief to the African continent, where in 2021 96% of the 619,000 people, including 475,000 children, died of malaria worldwide were concentrated. Marketed by the Serum Institute of India by 2024, R21 “should result in a sufficient supply of vaccines”, promises the head of the WHO. According to the GAVI White Paper, published in April, it will nevertheless take several years to structure the market so that it can meet demand. To compensate for this shortage, GAVI announced that the Mosquirix vaccine, initially developed and produced by GSK, will soon be manufactured in India by Bharat Biotech following a gradual technology transfer.
In the meantime, WHO has set up a specific framework in 2022 with representatives from the continent, including the African Center for Disease Surveillance and Prevention (Africa CDC), to determine priority countries and analyze the data in the field as vaccination campaigns are rolled out in the twelve beneficiary countries.
“The gap between supply and demand for malaria vaccines shows once again that Africa is almost entirely dependent on the North for research and on Asia for manufacturing,” laments Francine Ntoumi, epidemiologist and coordinator of the Central African Network on Tuberculosis, HIV and Malaria (Cantam). This is the time for the African Union (AU) and our States to learn the lessons of the Covid-19 crisis and put words into action by urgently developing our vaccine production capacities. Overcoming malaria is first and foremost our responsibility. »
Despite the AU’s ambition to meet 60% of the continent’s vaccine needs by 2040 and the projects launched, including the regional vaccinopole of the Pasteur Institute in Dakar, the continent was only producing in 2022 1% of the vaccines he consumes.
A new species of mosquito
Prevention is all the more crucial as problems accumulate in the areas of screening and treatment. Researchers have revealed that more and more parasites are going undetected by rapid diagnostic tests. Cohorts of sick people who are unaware of each other and untreated become vectors of the disease, in turn contaminating mosquitoes, which contaminate other humans. A situation that is “very worrying,” points out Didier Ménard, especially since control of the endemic is elusive due to new outbreaks of resistance to artemisinin, a key molecule in the treatment of patients, which have appeared in Rwanda and Uganda. and in the Horn of Africa”.
Eritrea and Ethiopia are particularly scrutinized, the two countries concentrating all the biological threats: resistance to artemisinin in Plasmodium falciparum, the species responsible for the majority of deaths, but also resistance in mosquitoes, vectors of disease, insecticides and the colonization of the African continent by a new species, Anopheles stephensi. The mosquito from the Middle East and Asia, carrying the two strains of plasmodia (falciparum and vivax) most dangerous to the human body, spreads rapidly at altitude and in cities, areas that are more spared, and is particularly insensitive. larvicides and insecticides.
Impregnated mosquito nets and insecticide sprays still have a bright future ahead of them, especially since they “are not used to their maximum potential, while these tools remain extremely effective and inexpensive”, insists Francine Ntoumi, which denounces the lack, or even the decline, of investments by certain African states in the control strategies highlighted in the latest WHO report, in December 2022.
