A vaccine for malaria now exists, marking a significant advancement in the global fight against this parasitic disease. This development is a scientific breakthrough, offering a new tool to prevent illness and save lives, particularly among young children in regions heavily affected by malaria. The introduction of this vaccine signals a shift in malaria control strategies, complementing existing interventions.
The First Malaria Vaccine
The first malaria vaccine recommended for widespread use by the World Health Organization (WHO) is RTS,S/AS01, known as Mosquirix. This vaccine is the result of decades of research and development, primarily led by GlaxoSmithKline (GSK) in collaboration with the PATH Malaria Vaccine Initiative (MVI). Its development began in 1987, with initial human studies in 1992 and the first trial in a malaria-endemic country in 1998.
A large Phase 3 efficacy and safety trial was conducted from 2009 to 2014, involving thousands of children across seven African countries. These extensive trials provided the data that informed the WHO’s recommendation. In 2015, the European Union’s drugs regulator approved the vaccine, making it the world’s first licensed malaria vaccine. The WHO officially recommended its widespread use for children in regions with moderate to high malaria transmission on October 6, 2021, following positive results from pilot implementation programs in Ghana, Kenya, and Malawi.
How the Vaccine Works
The RTS,S/AS01 vaccine targets Plasmodium falciparum, the deadliest malaria parasite in humans. Specifically, it focuses on the circumsporozoite protein (CSP) found on the surface of the parasite in its pre-erythrocytic stage. This stage occurs when the parasite, transmitted through a mosquito bite, first enters the human bloodstream and travels to the liver cells.
As a recombinant protein vaccine, it incorporates components of the Plasmodium falciparum circumsporozoite protein, a portion of a hepatitis B virus protein, and a chemical adjuvant. This combination prompts the immune system to produce antibodies and T-cells that can recognize and attack the malaria parasite. By inducing a strong immune response against the CSP, the vaccine helps to prevent the parasite from infecting liver cells, thereby stopping the infection before it can progress to the blood stage and cause widespread disease.
Targeting and Impact
The RTS,S/AS01 vaccine is recommended for children aged five months and older in regions with moderate to high Plasmodium falciparum malaria transmission, primarily in sub-Saharan Africa. It is administered as a four-dose schedule, with the first three doses given monthly and a fourth booster dose recommended around 15 to 18 months of age. This targeted approach ensures that the vaccine reaches the population most vulnerable to severe malaria and mortality.
Pilot implementation programs in Ghana, Kenya, and Malawi have demonstrated the vaccine’s significant public health benefits. These programs, which administered over 6 million doses between April 2019 and December 2023, showed a 13% reduction in all-cause mortality among eligible children and a 22% reduction in hospitalizations due to severe malaria. Mathematical modeling suggests that for every 100,000 children vaccinated, over 116,000 clinical malaria cases and nearly 500 deaths could be averted. The vaccine has shown to be feasible to deliver through routine childhood immunization programs, increasing equitable access to malaria prevention.
Limitations and Continued Efforts
While a significant step forward, the RTS,S/AS01 vaccine does not offer complete protection against malaria, and its efficacy can diminish over time. After a four-dose regimen, the vaccine’s efficacy against clinical malaria is around 36% over four years in children aged 5-17 months. The protection is lower in infants aged 6-12 weeks at the time of their first vaccination. This waning efficacy necessitates a multi-pronged approach to malaria control.
The vaccine is considered a complementary tool, not a replacement for established malaria control measures such as insecticide-treated bed nets, indoor residual spraying, and prompt diagnostic testing and treatment. Ongoing research pursues the development of new and more effective malaria vaccines. One notable candidate is R21/Matrix-M, which has shown higher efficacy rates, reaching up to 77% in initial trials, and has also received a WHO recommendation. These continued efforts highlight the commitment to further strengthen the arsenal against malaria.