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New vaccine could help end malaria
The tropical disease kills more people annually than cancer, but researchers think they can win the fight.
Last Modified: 11 Jan 2012 17:53
Ninety per cent of malaria cases are found in sub-Saharan Africa [Credit: World Health Organisation]

Dividing her days between treating malaria in Kenya's coastal regions and administering the latest malaria vaccine prototype, doctor Patricia Njuguna has high hopes for preventing a disease that annually claims more lives than cancer.

The vaccine which Njuguna is testing, known as RTS,S, has been heralded as one of the Top 10 Scientific Breakthroughs of 2011 by Time and Science magazines, Doctors Without Borders and the Lancet. It has been developed over the last 25 years as a joint public-private collaboration by GlaxoSmithKline Biologicals and the PATH Malaria Vaccine Initiative (an international non-profit organisation) with grants from the Bill and Melinda Gates Foundation.

Malaria is the oldest documented diseases known to man, dating back several million years. It is a potentially life threatening sickness caused by the single cell parasite Plasmodium. Transmission to humans occurs via mosquito bite, causing relapsing fevers with chills, flu-like symptoms and anemia. According to the World Health Organisation's (WHO) World Malaria Report 2011 released in December, 650,000 malaria deaths occurred in 2010, almost all in children under age five, the majority in sub-Saharan Africa.

Until recently, efforts to control malaria have been aimed largely at preventing mosquito bites and treating clinical disease. The word eradication was seldom used in conjunction with malaria; the idea of a vaccine to create immunity was a scientific dream, far from viable.

"I became involved because I strongly believe in prevention and have always been impressed by [the] impact of vaccines on disease burden," Njuguna told Al Jazeera. "I am hoping this will be the difference between control of malaria and the end of malaria."

Development of the first vaccine

Why has the production of a vaccine been such a challenge? There are at least four species of Plasmodium that cause malaria in humans, and the malaria parasite is notoriously adaptable.

"There has never before been a vaccine that targets any parasite. Unlike bacteria and viruses for which we've developed vaccines, the life cycle of a parasite is more complex," explains Dr Vasee Moorthy, technical officer for the Malaria Vaccine section at the WHO in Geneva. "Additionally, with malaria, even after being infected, one can still be infected again. It's a completely different ball game." 


Malaria vaccine trials in Kenya

In 2006, a group of 250 of the world's top malariologists drafted the Malaria Vaccine Technology Roadmap. The goal: To have a malaria vaccine that provides protection against the disease in 50 per cent of infants by the year 2015 and in 80 per cent of infants by 2025.

In late trials, the new RTS,S vaccine which Njuguna is testing has prevented transmission of the disease in 55.8 per cent of subjects, which is on target for the Roadmap.

"If this succeeds, which it is showing signs of doing, it would be a huge breakthrough," Dr Didier Leboulleux, Associate Director of the RTS,S Clinical Unit in Paris, France, told Al Jazeera.

The final results of the trial are to be released by 2014, and if these promising numbers continue, the WHO has plans to recommend use of the vaccine by 2015.

What is further remarkable about this achievement is that the scientists, physicians and epidemiologists who conducted the trials - with 15,000 participants in seven countries - are largely from Africa. Previously, the general consensus was that Africa did not have the capacity to run a study of this magnitude. 

"In terms of financial resources, we have needed help. But as far as intellectual resources go, there has been a lot of untapped talent within Africa that we have drawn on," says Dr Njuguna. "Just being an African researcher or scientist, you feel like you're helping to answer the questions that are relevant to your local community."

Ninety per cent of malaria cases are found in sub-Saharan Africa. Six countries - Nigeria, the Democratic Republic of Congo, Burkina Faso, Mozambique, Cote d'Ivoire and Mali - account for 60 per cent, or 390,000, of global malaria deaths per year. For a disease with such tremendous impact, it has received surprisingly little attention, largely because of its history as a disease of the developing world.

"I think it's fair to say that if malaria had been killing commuters in Washington the way it has been ravaging West African villages, we would have seen research, solutions and intervention much earlier," says Dr Richard Cibulskis, lead author of the World Health Organisation (WHO) World Malaria Report 2011.

Prevention strategies

While the RTS,S vaccine represents the attempt that is furthest along in clinical trials, an additional 30-50 labs around the world are feverishly working on concurrent vaccines.

Why so many? There are multiple species of malaria, each with a unique lifecycle, unique biochemical structure and different defences against our immune system.

 

Malaria life cycle with potential vaccine targets

 

Thus, separate vaccines, are being developed for different species, targeting different stages of their life cycle. It will be interesting to see which methods are more successful and which targets are effective. 

Indeed it is an exciting time to be a malariologist.

Until an effective vaccine is widely available, however, malaria still represents a significant global disease burden. Five per cent of African children are killed by malaria - almost 3,000 each day. Those involved with the vaccine are quick to point out that researchers are still a long way away from complete eradication.

"While this is extremely exciting for us, the main gains in the fight against malaria to date have come from better use at the local level of effective drugs, rapid diagnostics, mosquito nets and insecticides. The vaccine is not a replacement for those, and would be a complementary agent with the methods we have successfully used thus far," warns Dr Lee Hall, Chief of the Parasitology and International Programs Branch at the US-based National Institute of Health.

The key players in the fight against malaria thus far have been simple preventive strategies such as hygiene education, mosquito nets, insect repellants and insecticides. Additionally, drug therapy (both for treatment and prevention) has been successful. These interventions have decreased malaria related deaths by 25 per cent since 2000. In 2010 alone, malaria deaths fell by 36,000 compared to 2009.

Malaria interventions are highly cost effective and inexpensive. Insecticidal nets cost $1.39 per person per year of protection and it is estimated that 50 per cent of households in sub-Saharan Africa have at least one. A course of drug therapy costs between $0.30 - 0.40 for a young child, and $0.90 - 1.40 for an adult.

Ongoing efforts

The gains that have been made are tenuous; current interventions require ongoing support. Nets need to be replaced every three to five years. Insecticide resistance is beginning to develop, and rates of drug resistance are increasing. New drugs like artemesinins - the latest member of the treatment family discovered in 2006 - initially overcame this, but resistance to these drugs is starting to develop as well. Additionally, the availability of affordable, generic drugs is being threatened as pharmaceutical companies launch lawsuits to increase the rights of their patents.

"These are hard fought wins that can easily be lost. For example, if access to bed nets were to be lost, rates would start to increase," says Sally Ethelston, director of communications at the PATH Malaria Vaccine Initiative.

"I think it's fair to say that if malaria had been killing commuters in Washington the way it has been ravaging West African villages, we would have seen research, solutions and intervention much earlier"

Dr Richard Cibulskis, World Health Organisation

An estimated five to six billion dollars is needed annually to achieve malaria targets, according to the WHO. In 2010, there was $1.7bn committed to the cause, increasing to $2bn in 2011.

But the good news ends there. Funding for malaria will decrease in 2012, and is estimated to continue to decrease to $1.5bn annually by 2015. This is largely through lack of funding for the Global Fund to Fight AIDS, Malaria and TB by the international community, notably G8 and G20 members who are reneging on previously made financial commitments.

In April 2010, the UN met with a resolution to reduce malaria deaths to near zero by the year 2015. Their goal is ambitious, but not impossible.

In October 2011, the WHO certified Armenia as malaria-free, making it the fourth country in five years to be certified. The other three were the United Arab Emirates in 2007, Morocco in 2010, and Turkmenistan in 2010.

Cibulskis is wary but optimistic. "If we take the foot off the accelerator, we will see the rates of malaria rise. However, we've been living with malaria since human beings evolved. At each step in our fight there have been obstacles, and through our commitment and research we have overcome these. In 2000, we felt that malaria was in charge. These days, there is a belief that we can do something about it."

Follow Meera Dalal on twitter @MeeraDalal

Source:
Al Jazeera
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