Historic yet imperfect. That’s how I think of the World Health Organization’s recent endorsement of the long-awaited malaria vaccine, officially known as RTS,S/AS01, or simply as RTS,S.
This recommendation follows careful determination by two of the WHO’s high-level advisory panels, one on immunization and another on malaria, that RTS,S provides significant protection against disease and deaths and that it is safe and cost-effective.
That’s a huge step forward for a disease with 230 million cases in 2019, the last year with compete statistics, one that killed 409,000 people. Although malaria is most common in sub-Saharan Africa, it is also endemic in southeast Asia, the eastern Mediterranean, western Pacific, and Central and South America.
The WHO’s final recommendation follows an ongoing pilot program in Ghana, Malawi and Kenya, in which 2.3 million doses have already been given to more than 800,000 children. This program demonstrated that RTS,S can be delivered alongside other childhood vaccines, and that its introduction does not interfere with other malaria intervention programs.
Countries in which malaria is endemic can now include the vaccine as one of the interventions for children starting at age 5 months. It is set to be given in four doses, the first three given monthly and the last dose two years later to boost immunity against repeat infections. Children in endemic areas typically suffer multiple infections, so this booster dose is particularly crucial.
Since RTS,S is the first-ever malaria vaccine, and the first vaccine against any parasitic disease, its approval is historic. A widely accepted vaccine development roadmap currently has set targets of 75% protection against malaria cases and 50% protection against deadly forms of malaria. Both of these targets, however, are far above the protection that RTS,S offers — hardly exceeding 40% against malaria cases or 30% against deadly severe malaria — making RTS,S also imperfect.
Although there has been talk in recent years about malaria elimination, actual progress has been slow. Starting in 2000, greater investments in fighting malaria have averted an estimated 1.5 billion malaria cases and 7.6 million deaths, yet population growth and a myriad of other challenges in sub-Saharan Africa have left the total malaria burden unchanged. In fact, since 2015, many of the countries with the highest malaria burden have recorded increases in cases.
The WHO emphasized that this vaccine should be viewed as just one component in the arsenal against malaria and must be considered in a broader context of ongoing malaria control efforts. Countries must continue using existing malaria interventions such as artemisinin combination treatments, insecticide-treated bed nets, and preventive treatments for pregnant women and children because RTS,S is no silver bullet.
This raises questions about how the adoption of RTS,S may change the malaria control landscape, whether the vaccine will be affordable, whether there will be adequate doses to go around, and who will finance the vaccine programs. Countries adopting RTS,S may therefore wish to prioritize areas of highest burden, where the vaccine is expected to yield maximum impact.
No matter what malaria-prevention strategies countries select, the benefits of RTS,S will be accrued only if governments enhance the basic infrastructure of their health systems to enable effective vaccine delivery. That it takes four doses per child will create an additional layer of complexity and potentially reduce overall effectiveness. Fortunately, the ongoing pilot studies suggest that the RTSS vaccine can be readily integrated into the expanded programs of childhood immunizations (EPIs), without negatively impacting other malaria interventions. These EPI programs are already widely popular in Africa and are among the most cost-effective.
Other than the governments of countries in which malaria is endemic, major financers of malaria control today include The Global Fund, created in 2002, and the U.S. President’s Malaria Initiative, created in 2005. Most of the funding may have already been earmarked for existing tools, so the introduction of RTS,S is expected to initiate in-depth negotiations for either additional fundraising or reprograming of available budgets.
The Global Vaccine Alliance (GAVI), which has been an extraordinary champion of childhood vaccination — and most recently Covid-19 vaccination — in low-income countries will also likely play a crucial role in negotiating the financing, procurement, and delivery of RTS,S.
Beyond RTS,S, other candidate anti-malaria vaccines are currently in advanced trials. These include the sporozoite vaccines, which require injection with live malaria parasites followed by a prophylactic dose of chloroquine to ensure that the person does not develop actual disease but remains sufficiently protected against future infections. There is also the R21 vaccine, which recently showed up to 77% protection in a small trial involving 450 children in west Africa, and is scheduled for larger trials. Perhaps most exciting has been the recent announcement by BioNTech that it will configure the mRNA technology behind its successful Covid-19 vaccine to target the malaria parasite.
These options have different advantages and disadvantages, and will be crucial next steps in the now-rejuvenated malaria vaccine era. It is imperative that all promising options are accelerated to make up for all the years during which malaria innovation has been so excruciatingly slow.
Malaria endemic countries must resist the temptation of seeing RTS,S as a one-and-done solution and instead consider multiple options and formulate context specific packages of interventions for maximum impact. They must continue building more holistic strategies consisting of stronger health systems and multi-sectorial initiatives necessary to sustain the gains; as well as the pursuit of potentially transformative tools to accelerate anti-malaria efforts.
As the first vaccine against a parasitic disease, one that was evaluated widely by African scientists, RTS,S could inspire new interest in public health and herald greater commitments to malaria control. Going forward, African countries should marshal greater energies to advance innovation against priority health challenges.
The journey toward zero must not end here and the WHO’s endorsement of RTS,S vaccine must not drive complacency. Instead it should inspire greater focus on achieving malaria elimination as fast as possible and with as few deaths as possible using every available strategy.
Fredros Okumu is mosquito biologist and public health expert, director of science at Ifakara Health Institute in Tanzania, and an Aspen Institute New Voices Fellow. He is a member of the WHO Malaria Policy Advisory Group, which evaluated RTS,S, and reports having received research funding from the Bill and Melinda Gates Foundation and the Wellcome Trust, among others. The views expressed here are his own, and not to be viewed as representing any of the organizations with which he is affiliated.
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