World Health Organization just approved a new vaccine that, according to the scientific community, will constitute a turning point in the fight against malaria, which each year kills half a million people in Africa.
The vaccine R21/Matrixdeveloped by the University of Oxford in collaboration with the Serum Institute of India, has high efficacy, low production cost and can be manufactured on a large scale.
Why is it a turning point?
According to the research we are carrying out, this vaccine is about 75% effective in terms of reducing the number of malaria episodes in the time frame of one year. The best vaccine so far was 50% effective in that same period of time, and a decreasing percentage in the following three years.
This is a very significant improvement, but it is not the only one. The big difference lies in the fact that it can be manufactured on a scale that responds to the need to protect the majority of children who require vaccination against the disease in Africa.
Every year about 40 million children are born in malaria-stricken areas of the continent who could benefit from the vaccine. Ours is administered in four doses in 14 months, so 160 million of them are needed. It is something viable.
The Serum Institute of India, our manufacturing and commercial partner, has the capacity to produce hundreds of millions of doses of this vaccine per year, while in the case of the previous vaccine six million doses could be manufactured per year between 2023 and 2026, according to UNICEF in its reports.
The third, substantial advantage of this vaccine is the cost. We knew perfectly well that we could not produce a vaccine that cost 100 dollars (95 euros). It would not be profitable for international agencies to purchase and distribute the vaccine in low-income countries. Now we have a price that will vary depending on the scale of production; in a high volume, each dose should cost $5 (4.75 euros).
Why has it been so difficult to develop a malaria vaccine?
For more than 100 years, the scientific community has tried to develop vaccines against this disease. Clinical trials have been conducted with individuals with more than 100 vaccines. Almost none have had any effect.
Malaria is not a virus, nor is it a bacteria. It’s a protozoan parasite, several thousand times larger than a common virus. A good way to account for its nature is to count how many genes it has. The virus that causes covid-19 has 13; the malaria parasite, about 5,500. This is one of the reasons for its extreme complexity.
Parasites take on different forms in their life cycle. The first of them is transmitted by the mosquito through a bite in the dermis, and it quickly spreads to the liver. There, the parasites proliferate for a week, then enter the bloodstream. These microorganisms increase ten times their size every 48 hours and multiply exponentially.
At the moment they reach a high parasite density, the infected person begins to notice the first serious symptoms. In the worst cases, the patient can die, usually as a result of damage to the brain, coma or severe anemia. Parasites are responsible for the breakdown of red blood cells.
In another phase, the parasite once again acquires the form transmissible by the mosquito to continue its life cycle infecting other individuals.
Malaria usually has four life cycles, all completely different. If you get a vaccine good enough to stop one of these cycles, you can stop the chain of transmission. That is precisely what we have tried to achieve.
We have been working to attack sporozoites, that is, the phase in which the mosquito transmits the disease through the skin. What we are trying to do is stop transmission before they reach the liver to reproduce and continue their life cycle.
Fortunately, in this phase the typical symptoms of malaria do not appear. The infection is silent until it reaches the blood and the microorganisms begin to multiply inside the red blood cells.
At the time, scientists tried to use the microorganism in the same way that Edward Jenner, a pioneer in the field of vaccinology, used the smallpox virus, in its complete form, to develop a vaccine. Later, French microbiologist Louis Pasteur developed bacterial vaccines. In 1943, a trial with a possible vaccine from the entire malaria parasite was carried out in New York, but without results. These failed attempts created a climate of mistrust.
It was not until the 1980s when we were able to begin sequencing the parasite’s genes and when the first vaccines with potential began to emerge. In the next 10 years, there were 5,000 promising vaccines, as all scientists hoped that the gene they had sequenced would be the vaccine against the disease. Of course, most of them didn’t work out.
Why do vaccines for whole parasites have no effect against malaria?
For the same reason that getting infected with malaria once does not protect you from the next infection.
In the disease-hit areas of Africa where we test our vaccines, some children suffer up to eight episodes in three or four months. Natural immunity does not work until a person contracts multiple different infections, and that explains why adults are generally protected against malaria and do not usually develop very serious symptoms.
In endemic areas they are Small children those who die from malaria as a consequence of the first infection or because they have not acquired immunity despite having suffered one or two episodes.
Malaria has lived with us for tens of millions of years. Not only with humans, but also with the species we were before we became humans.
It is a very cunning parasite that has developed mechanisms of all kinds to evade immunity.
When you try to administer a vaccine, you realize that the parasite always finds a way to escape. It is only possible to fight it when extremely high levels of antibodies develop that the microorganism has not detected and does not know how to get around.
Can we completely eradicate malaria from the face of the Earth?
Malaria occupies one of the highest steps on the list of diseases we want to eradicate. I don’t think that in the next five or 10 years, we will achieve it, but within 15, more or less. Therefore, 2040 seems a reasonable date.
Nobody is saying to stop using mosquito nets, insecticides, or medications. But what we have now is a new tool that will protect people more than any of the mechanisms we use today.
This article has been translated with the collaboration of Africa House. Translation: Eduard Galán.
2023-10-15 22:58:29
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