The rollout of malaria vaccines in Africa – the world's first routine immunization program against this mosquito-borne disease – has raised excitement for a surprising reason. The vaccine reduces all kinds of deaths among children – not just malaria deaths – by 13%.
This RTS,S vaccine is "not only a huge step forward for malaria control but also a major advancement in child health," says Dr. Mary Hamel, the World Health Organization's senior technical officer on malaria, in an email interview with NPR.
The 13% statistic came from a successful WHO pilot campaign in Ghana, Kenya and Malawi, where over two million children from age 5 months to 2 years have received the malaria vaccine since 2019. Developed by the pharmaceutical company GlaxoSmithKline, the RTS,S vaccine prevented about 39% of malaria cases and 32% of severe cases in Phase 3 trials, as compiled by WHO.
"While 39% efficacy seems low for a vaccine, when we consider the sheer burden of malaria, this means potentially a huge reduction in cases and deaths among children," said Dr. Aaron Samuels, CDC's Kenya malaria program director, in 2021.
Indeed, in 2022, there were an estimated 249 million cases of this mosquito-borne disease globally and 600,000 deaths. Africa was home to 95% of these deaths, including almost half a million children under 5.
The new vaccine does present some challenges: children need four doses over a year to be fully vaccinated, which may be difficult to coordinate outside of clinical trial settings. A huge quantity will be needed, and each dose costs about $9.80. There had been concerns about getting an adequate supply from pharma company GSK. But the approval of a second malaria vaccine by WHO, called R21/Matrix-M, should help address shortages in vaccine coverage since it requires only 3 doses, each costing $2-4, with 100 million doses expected to be available later this year.
The RTS,S vaccine campaign began on Monday in Cameroon, with the goal of reaching 6.6 million children across 20 African countries by 2025. Dr. Kate O'Brien, director of the Department of Immunization, Vaccines and Biologicals at WHO, expects the scale-up of the malaria vaccine will save tens of thousands of lives annually.
An unexpected bonus
Certainly, some of these averted deaths will be directly related to malaria. But the unexpected development is that the vaccine seems to reduce deaths where malaria is only a contributing factor, exacerbating other diseases but not killing the patient itself, according to Dr. Steve Taylor, a global health and infectious disease expert at Duke.
As an example, he notes that contracting malaria makes you more likely to get salmonella disease – the most common bloodstream infection in Africa with a case fatality of up to 20-25%. Malaria also seems to make people susceptible to bacterial infections more broadly, with a Lancet study out of Eastern Kenya in 2011 demonstrating that over half of bacteremia cases were attributable to malaria.
In an email to NPR, Hamel also describes how children who have HIV or face chronic malnutrition are at higher risk of severe malaria, which in turn can exacerbate HIV and malnutrition, potentially leading to death. "We have seen this before with malaria," she says, in trials where children got insecticide-treated nets or preventive antimalarial tablets, "that the reduction in mortality is more than what one would expect from a decrease in malaria deaths alone."
Decreasing non-malaria deaths is not the only spillover benefit of the vaccine. Malaria is a "major reason for school absenteeism, anemia and impaired cognitive development," said Dr. Mohammed Abdulaziz, head of disease control and prevention at Africa CDC, at the press conference. "This vaccine is a crucial element in improving African children's educational outcomes and cognitive ability, which can help break the cycle of adversity plaguing our youth."
A welcome development but not a 'magic bullet'
This vaccine also comes at an important time as malaria caseloads have been steadily increasing from 209 to 233 million in Africa between 2000-2022. "We've had resurgences of malaria in a lot of places and particularly during the pandemic," says Dr. Chris Plowe, a malariologist at the University of Maryland. "A lot of progress that was made in the first part of the 21st century has plateaued and, in some places, reversed." Climate change, for instance, has contributed to increased malaria exposure in sub-Saharan Africa, and growing drug and insecticide resistance has made fighting malaria more difficult.
"The parasite is so plastic, so malleable, so quickly able to evolve all these interventions," Plowe continues. "If you let up pressure, it will evolve, it will change, it will come back."
So, while malaria experts are celebrating the vaccine, it needs to be part of a preventive program with mosquito nets and other existing tools, said Dorothy Achu, lead for tropical and vector-borne diseases in the WHO Regional Office for Africa, at the press conference. "In the malaria community, we always say we do not have any magic bullet."
That's why experts were reassured to see that, in the pilot campaign, the vaccine didn't reduce the use of insecticide-treated bednets, people's willingness to seek malaria treatment, or uptake of other childhood vaccines because parents thought the malaria vaccine was sufficient and it was fine to skip the others, according to O'Brien from WHO. While the RTS,S vaccine itself may only prevent 30-40% of malaria cases, this number rises to 90% when combined with mosquito nets and protective malarial tablets, according to a Lancet Infectious Diseases study from 2023.
This expanded protection is why the malaria vaccine will usher in a "transformative chapter in Africa's public health history," Africa CDC's Abdulaziz told reporters. "For a long time, we have been waiting for a day like this. It brings more than just hope. It brings a reduction in the mortality and morbidity associated with malaria."
Simar Bajaj is an American journalist who has previously written for The Atlantic, TIME, The Guardian, Washington Post and more. He is the recipient of the Foreign Press Association award for Science Story of the Year and the National Academies award for Excellence in Science Communications.