Developing an effective malaria vaccine has proven much more difficult than developing a vaccine to protect people from COVID-19. Several vaccines against COVID-19 were developed and approved for use within a year of the onset of the disease.
Instead, it took more than 30 years of intensive research and numerous clinical trials by the Walter Reed Army Research Institute and its partners before the first malaria vaccine, Mosquirix, was approved for the World Health Organization (WHO) in 2021.
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Creating a vaccine for a vector-borne disease like malaria is very difficult. The parasite takes different forms in different hosts. And it is constantly evolving to evade the human immune system and control interventions.
In an important step towards the equitable deployment of Mosquirix, the WHO granted prequalification status for the vaccine in September 2022. The prequalification step follows approval. It ensures that only good quality products are procured and distributed by UN agencies and other major donors.
More recently, researchers in Burkina Faso and the University of Oxford’s Jenner Institute, the same institution that developed the Oxford/AstraZeneca COVID-19 vaccine, made their own revelation. They published very encouraging data from a clinical trial evaluating the new R21 malaria vaccine.
Like Mosquirix, the R21 vaccine targets the sporozoite. This is the stage of the malaria parasite that is transferred to humans when the malaria-infected female Anopheles mosquito takes a blood meal. When effective, both vaccines ensure that the sporozoites are destroyed before they enter the liver. It effectively prevents malaria infection by stopping the life cycle of the parasite in the human host.
The fight against malaria has been significantly strengthened with the addition of malaria vaccines to the package of prevention measures. These vaccines have the potential to reduce malaria-related illness and death in children under five, one of the populations most affected by malaria today.
What the studies show
Both vaccines, Mosquirix and R21, target the same parasite stage and use the same malaria proteins. But Oxford’s R21 vaccine contains a higher number of these malaria proteins. And it uses a different adjuvant: a chemical that stimulates the body’s immune response. These two factors are thought to enhance the effectiveness of the R21 vaccine by eliciting a stronger immune response.
The preliminary data is drawn from a two-year study involving 409 children aged five to 17 months. The children received a booster dose 12 months after receiving the first three doses of the vaccine. The data suggest that the R21 vaccine resulted in a higher level of protection than Mosquirix.
Eight out of 10 children who received four doses of the R21 vaccine did not develop malaria during the trial period, making this malaria vaccine the first to meet the WHO’s minimum effectiveness target of 75% over 12 months in the target population of African children. .
The results of these studies are encouraging.
But researchers have cautioned against a direct comparison between the performance of the R21 and Mosquirix vaccines. Unlike the Mosquirix vaccine, the R21 vaccine was given to children before the start of the malaria season. And it was only tested on a small number of children in one region of Burkina Faso. In addition, various control and prevention measures have been implemented.
A larger study is needed to confirm the effectiveness of the vaccine in African children across the continent. This study should be done in regions with different intensities of malaria transmission, different levels of malnutrition and anemia in the target populations and different coverage of control interventions.
Four thousand eight hundred children from four African countries, two of which have year-round malaria transmission, have been enrolled in a phase 3 clinical trial. The goal of this trial is to demonstrate the safety and vaccine effectiveness in a larger and more diverse group of children. Jenner Institute researchers hope the R21 vaccine will be approved for use next year, provided no unexpected safety issues arise in this larger trial.
Manufacturing and distribution bottlenecks prevented the timely and equitable distribution of COVID-19 vaccines. To prevent a repeat, Oxford University has signed a manufacturing agreement with the Serum Institute of India, the world’s largest vaccine manufacturer. Under this agreement, the Serum Institute has committed to supply at least 200 million doses annually. That’s far more than the 15 million to 18 million doses of Mosquirix that GlaxoSmithKline is contracted to produce each year through 2028.
But, according to the WHO, this amount is much lower than the expected demand for vaccines. To increase manufacturing capacity, the Jenner Institute is in talks with African vaccine manufacturers.
Moving forward
Manufacturing the vaccines is only the first step.
Other obstacles include ensuring that countries can procure the vaccines, that there is equitable delivery of vaccines to requesting countries, and that there is rapid distribution of vaccines to all health facilities within malaria risk areas. And most importantly, that there is an optimal absorption of the vaccines.
Misinformation, vaccine vaccinia, and safety concerns have contributed to a lower rate of vaccination against COVID-19, especially among children.
For a malaria vaccine to have an impact, health promotion is key. Awareness campaigns should address safety concerns while emphasizing the expected positive impacts of the vaccine. These campaigns should target both health professionals and affected communities. They should be delivered before and during the vaccine launch to ensure that any new misinformation or concerns are addressed quickly and effectively.