A first vaccine falling victim to its own success, a second one about to come into the picture: 2023 is a decisive year in the fight against malaria. After 20 years of progress, malaria research has been at a standstill since 2020, but the deployment of the RTS,S (or Mosquirix) serum from British giant GSK, and the arrival of R21/Matrix-M, developed by Oxford University and recommended on Monday, October 2 by the World Health Organization (WHO), promise to turn the tide. By 2030, the WHO and the Global Alliance for Vaccines and Immunization (GAVI) anticipate demand for up to 100 million doses, the two institutions stated 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 entering the bloodstream. In that way, they are an invaluable tool," explained Didier Ménard, professor of parasitology at the University of Strasbourg and member of the "Malaria genetics and resistance" unit at the Institut Pasteur in Paris.
Following the success of the pilot phase that was started in 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 soared. Thirty African countries applied to benefit from its large-scale deployment, but only 12 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, sharing the 18 million doses produced for the period 2023-2025. "This is an unprecedented level of demand," said Tedros Adhanom Ghebreyesus, WHO director-general.
The second vaccine should help bridge the gap and bring relief to the African continent, which accounted for 96% of the 619,000 people, including 475,000 children, who died of malaria worldwide in 2021. Marketed by the Serum Institute of India by 2024, R21 "should translate into a sufficient supply of vaccines," promised the head of the WHO. However, according to GAVI's White Paper published in April, it will take several years to structure the market to match demand. To bridge the gap, GAVI has announced that the Mosquirix vaccine, initially developed and produced by GSK, will soon be manufactured in India by Bharat Biotech, following a gradual transfer of technology.
In the meantime, the WHO has established a specific framework in 2022 with representatives from the continent, including the African Centres for Disease Control and Prevention (CDC Africa), to identify priority countries and analyze field data as vaccination campaigns are rolled out in the 12 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 Asia for manufacturing," said Francine Ntoumi, epidemiologist and coordinator of the Central African network on tuberculosis, HIV, and malaria (Cantam). "It is time for the African Union (AU) and our member states to learn the lessons of the Covid-19 crisis and put their words into action by urgently developing our vaccine production capacities. Eradicating malaria is first and foremost our own responsibility."
Despite the AU's ambition to meet 60% of the continent's vaccine needs by 2040 and the projects it has launched, including the regional vaccine hub at the Institut Pasteur in Dakar, by 2022 the continent was producing just 1% of the vaccines it consumed.
Prevention is even more crucial as problems are piling up on screening and treatment. Researchers have revealed that more and more parasites are going undetected by rapid diagnostic tests. Untreated cohorts of unaware sufferers become vectors of the disease, in turn contaminating mosquitoes, which then contaminate other humans. This is a "very worrying situation," said Ménard, "especially as we are losing control of the endemic due to new outbreaks of resistance to artemisinin, a key molecule in the treatment of patients, which have appeared in Rwanda, Uganda, and the Horn of Africa."
Eritrea and Ethiopia are under particular scrutiny, as the two countries concentrate all biological threats: resistance to artemisinin by Plasmodium falciparum, the species responsible for the majority of deaths, but also the resistance of mosquitoes, the vectors of the disease, to insecticides and the colonization of the African continent by a new species, Anopheles stephensi. This mosquito from the Middle East and Asia, which carries the two most dangerous strains of plasmodia (falciparum and vivax) for the human organism, spreads rapidly at high altitudes and in urban areas, zones which are largely spared, and particularly insensitive to larvicides and insecticides.
Impregnated mosquito nets and insecticide sprays still have a bright future ahead of them, especially as they "are not being used to their full potential, even though these tools are still extremely effective and inexpensive," said epidemiologist Ntoumi, who condemned the lack of – or even backtracking on – investment by certain African countries in the control strategies highlighted in WHO's latest report, in December 2022.
Translation of an original article published in French on lemonde.fr; the publisher may only be liable for the French version.