WASHINGTON — The world’s first malaria vaccine may finally be within reach.
Scientists and public health officials are optimistic about recent news that a malaria vaccine candidate was able to reduce the risk of malaria by half in young African children in the first results of a Phase III trial. In 2009, malaria caused an estimated 781 000 deaths, mostly among African children, according to the World Health Organization.
The preliminary results of the trial, conducted in sub-Saharan Africa, were published online in the New England Journal of Medicine on Oct.18.
Known as RTS,S/AS01, the vaccine candidate has been in development since the 1980s and was initially developed as a result of work done by the Walter Reed Army Institute of Research and GlaxoSmithKline (GSK). The PATH Malaria Vaccine Initiative (MVI) and GSK have been studying the vaccine candidate’s ability to protect young children in sub-Saharan Africa with funding from the Bill & Melinda Gates Foundation.
The Phase III trial was launched in 2009 and has been conducted at 11 trial sites in seven countries across sub-Saharan Africa, including the U.S. Army Medical Research Unit Kenya. The trial indicated that three doses of RTS,S reduced the risk of children experiencing clinical malaria and severe malaria by 56% and 47%, respectively. This portion of the study included 6,000 children aged 5 to 17 months, who were followed over a 12-month period following vaccination.
In addition, preliminary analysis of severe malaria episodes in the 15,460 infants and children enrolled in the trial, age 6 weeks to 17 months of age, showed 35% efficacy over a follow-up period ranging between 0 and 22 months. All results are expected to be available by the end of next year.
“The RTS,S/AS01 study results, published in the New England Journal of Medicine, are a promising advance in development of a malaria vaccine for African children, which, if successful, could save hundreds of thousands of lives,” said CDC Director Thomas R. Frieden, MD, in a written statement.
CDC, in collaboration with the Kenya Medical Research Institute, led the trial at one site in western Kenya. “In 2009, malaria caused the deaths of nearly 800,000 people; approximately 90% were children in Africa.”First Malaria Vaccine Could Be Available in Four Years Cont.
The military’s search for a vaccine
WRAIR malaria expert Col. Christian F. Ockenhouse, MD, PhD, told U.S. Medicine that researchers there were, “pleased that such a vaccine has met and exceeded expectations,” and that the RTS,S vaccine represents “over two decades of collaborative partnership between WRAIR and GlaxoSmithKline.”
Ockenhouse said that WRAIR’s role in the co-development and advancement of the RTS,S vaccine included clinical testing of more than a dozen prototypes leading up to the phase 2 and 3 field studies of RTS,S in sub-Saharan Africa; first proof-of-concept clinical trial demonstrating protective efficacy of RTS,S against malaria challenge in subjects tested at WRAIR; first testing of RTS,S vaccine in Africa; improvements to the safety & efficacy of the vaccine by testing different adjuvant formulations with RTS,S first in non-human primates then in human volunteers; and current participation in the phase 3 clinical trial at WRAIR field site in Western Kenya.
The military has been keenly interested in the development of a malaria vaccine, because the parasite-borne disease also puts troops at risk. Without an FDA-approved malaria vaccine, deployed troops must completely rely on the use of antimalarial drugs, bed nets and other methods to repel potentially infected mosquitoes. While these preventive methods work, in theory, compliance can be a problem, and any breakdown in protocol can have serious implications.
While the military played a role in the development of the RTS,S candidate vaccine, it continues to search for a malaria vaccine that will suit the needs of troops. The U.S. Military Malaria Vaccine Program’s goal is to develop a vaccine that yields at least an 80% protection rate.
Because RTS,S, does not yield this protection rate against P. falciparum, WRAIR scientists are working with outside partners to see if they can improve the efficacy of RTS,S. In addition, other malaria vaccine approaches are being pursued by military researchers at the USMMVP.
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Further Study Results Expected
Public health officials have been eager to see a malaria vaccine developed because of the serious toll taken by the disease, particularly among children. According to the WHO, approximately half of the world’s population is at risk of malaria. In 2009, malaria was present in 108 countries and territories.
Still, public health officials will have to wait to determine the potential vaccine’s ultimate future. The Phase III trial is ongoing, and the safety results in 6- to 12-week-old infants are expected by the end of 2012. Further data on the long-term efficacy of the vaccine for both groups of children are expected to be in by the end of 2014.
“While all those involved in the trials are excited by the latest results in the 5- to 17-month age group, the efficacy of the population in the expected target population of 6 to 14 weeks is not yet known,” the WHO wrote in a written release on its website.
According to the WHO, if all required public health information from the trial is satisfactory, a WHO recommendation for use of the vaccine candidate could be possible as early as 2015.
In an editorial in the New England Journal of Medicine, Nicolas White, MD, a malaria expert at Mahidol University in Bangkok, Thailand, wrote that the trial result “is a great achievement and an important advance, but [the investigators] know that this partially protective vaccine is not the sole solution to the control and elimination of malaria.”
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