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Experimental Malaria Vaccine Shows Promise

by Guy McCardle

October 21, 2011

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Donate For the first time a vaccine has shown great promise in preventing one of the world’s biggest killers, malaria. More than half of the planet’s population is at risk of developing malaria. Each year the disease is responsible for approximately 800,000 deaths. Most of the victims are children under the age of 5 who live in sub-Saharan Africa. The vaccine, called RTS,S, offers partial protection, cutting episodes of malaria in babies and toddlers in half. Although not nearly as impressive as most vaccines currently in use, experts say this vaccine could help curtail malaria's massive death toll significantly.

The vaccine was developed by GlaxoSmithKline (GSK) Biologicals in partnership with the PATH Malaria Vaccine Initiative. It has been in development for more than 25 years, initially for the American military and now with most of its support from the Bill and Melinda Gates Foundation. The vaccine contains an engineered protein that combines a protein fragment from the malaria parasite, Plasmodium falciparum, and a protein from the Hepatitis B virus that helps trigger a strong immune response.

The trial, conducted at 11 sites across sub-Saharan Africa, showed that three doses of RTS,S reduced the chances of children experiencing clinical malaria and severe malaria by 56 percent and 47 percent respectively. The testing was performed on 6,000 children aged 5-17 months over a 12 month period following vaccination. Malaria results in high fever and chills. Untreated, it can develop into severe malaria. This is typified by damage to the blood, brain and kidneys that can prove fatal.

The trial is ongoing in 6-12 week old infants and will conclude in 2012. So far, a total of 14,560 children, enrolled in the trial between an age of 6 weeks to 17 months, have been evaluated. The data show a 35 percent efficiency rate for the vaccine over a follow up period of 0-22 months. Further information about the longer-term protective effects of the vaccine, 30 months after the third dose, should be available by the end of 2014.

But why does the efficiency rate of this vaccine seem so low when compared to others? Vaccines against viruses and bacteria usually have protection rates of up to 90%, but P. falciparum, an organism with a complex life-cycle, has proven to be a much more difficult target, which is why the vaccine should be combined with other strategies, such as bed nets, says Joe Cohen, who leads the malaria vaccine project at GSK Biologicals. "This vaccine will not be a magic bullet against what is a very, very difficult disease. It is one weapon to be added to an arsenal of other interventions."

When we look at any vaccines we automatically look at how safe they are. Is RTS,S safe? The overall incidence of serious adverse events (SAEs) in this trial was comparable between the RTS,S vaccine (18 percent) recipients and those receiving a control vaccine (rabies, with 22 percent SAEs). Particular types of SAEs, such as seizures and meningitis, were higher in the malaria vaccine group. Seizures were considered to be related to fever, and meningitis was considered unlikely to be vaccine-related. These events will continue to be monitored, and results will be published with the final report of the testing in 2014.

GlaxoSmithKline, which has invested more than $300 million in RTS,S to date, has pledged to keep the price as low as possible"just manufacturing costs plus a small return to be reinvested in development of second-generation malaria vaccines or vaccines against other neglected tropical diseases.


Publication of First Results in Ongoing Malaria Vaccine Trial Marks Important Milestone " MVI Path

Scientists See Promise in Vaccine for Malaria " The New York Times

Experimental malaria vaccine protects many children, study shows " The Washington Post

Malaria Vaccine Candidate RTS,S Reduces the Risk of Malaria by Half in African Children, Study Finds " Science Daily

Malaria Vaccine Meets (Modest) Expectations " Science Now

by Guy McCardle

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