WHO aims for licensed vaccine with 75% efficacy rate by 2030.
Malaria is a particularly nasty disease which inflicts over 200 million people worldwide. Even though several anti-malarial medications exist, the World Health Organization (WHO) predicts 660,000 people die from the disease each year. Death rates are diminishing, but not fast enough. So it seems we need a better strategy to fight this disease.
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That strategy is vaccination.
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Right now, there are 27 vaccine candidates in clinical trials. As clinical trials go, many of these candidates will fail to provide adequate protection. But there is still much optimism to go around. One vaccine candidate is nearing the finish line of clinical trials and is expected to be licensed by 2015. If proven successful, this vaccine will protect children under the age of 5 from a particularly deadly strain of the Pladmodium parasite that causes malaria.
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Another vaccine was recently celebrated in the news.
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This vaccine completed its first clinical trial with a success rate of 100% in patients who received the highest dosage number. Certain aspects of this vaccine differentiate it from the others. Many of the current vaccine candidates contain “subunits” of the Plasmodium parasite, but this vaccine contains an entire Plasmodium parasite which is weakened by radiation. Previously, scientists discovered this weaker form of the parasite led to protective immunity, but it was only through mosquito administration. To overcome this hurdle, the scientists in this study delivered the dosages through IV injections. This delivery option is unique. Most vaccines, such as the yearly flu shot, are administered intramuscularly, and many others are administered intranasally, subcutaneously (below the skin), intradermally (between layers of the skin), and orally.
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When the scientists examined the immune response of these protected patients, they made a surprising result. While the immune response increased with higher dosages of the vaccine, it remained weaker than responses seen with other “subunit” vaccines. The scientists suggest that the entire parasite might present more targets for the immune system to recognize, and therefore create multiple responses that are undetectable by the current tests. This new vaccine was discovered by a group of scientists at the Vaccine Research Center at the NIH and was published in the journal Science back in August. The scientists behind this vaccine sound hopeful in their discovery but mention their vaccine is still years away from development.
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The Parasite
Plasmodium is a difficult pathogen to fight against. This is due to its life cycle. Plasmodium is not spread by normal human contact; instead it relies on mosquitoes for passage. Since Mosquitoes are technically a bystander in the infection process, they are termed a “vector” for the parasite.
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The parasite resides in the mosquito’s saliva, which allows for transmission during a simple bite. Initially the parasite accumulates in the liver. From there, it expands in numbers and spreads to red blood cells. This is where the parasite causes the most harm. First, it multiplies inside a red blood cell and second, it breaks out of the cell and all the progeny search for new cells to invade.
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When the red blood cell ruptures, it releases different contents that signal the body’s immune system to turn on. This causes the “sick” feeling. Symptoms include: fever, headache, nausea, vomiting, and fatigue. If these symptoms remind you of the flu, then you are not alone. In fact, many cases of malaria are falsely diagnosed due to this mistake.
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If left untreated, malaria will eventually cause serious problems throughout the body, including:
- Cerebral damage leading to seizures and coma
- Kidney failure
- Anemia (red blood cell loss)
- Inability to balance levels of acidity and glucose in the blood
All of these problems can lead to death.
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Treatment
Fortunately, there are medications to cure malaria if taken before severe symptoms arise.
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This does not discount the need for a vaccine though.
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Providing proper patient consultation throughout the many poor areas in the world is very challenging. This is an important consideration because different strains of the parasite require different medication and certain medications work better depending on the status of the patient. Furthermore, certain strains of Plasmodium (mainly those found in Africa) are resistant to all of the known anti-malaria drugs.
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Aside from medications, efforts to derail the spread of Plasmodium are focused on mosquito control. This involves insect sprays and mosquito nets. While these steps are helpful, they are not perfect.
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Science to the rescue
The WHO announced in mid-November that it will lead a new push to create “next generation” vaccines which will target a broader pool of Plasmodium species. Their goal is to license a broad-ranged vaccine with a 75% success rate by 2030. To meet these goals, funding sources will focus on research that backs these enterprises.
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As a scientist, I feel optimistic about their efforts due to the multiple strategies and monetary focus being applied to fight malaria. Malaria is one of the major diseases in the world and to think it might be cured within our lifetime is an amazing thought.
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The Microbe Blog 
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I listened to podcast about this article on Science and it seemed like a very cool study. The way they captured the nonreplicating sporozoite and used as vaccine was interesting to me. Thanks for the review and all the information!