RTS,S offers 46 percent protection against malaria for at least 15 months after vaccination, Study finds

Jan 18 2011

A Phase II trial published Friday in Lancet Infectious Diseases has shown that RTS,S, the "experimental malaria vaccine from GlaxoSmithKline provides African children with long-lasting protection" against malaria, Reuters reports. "Scientists conducting the mid-stage trial at the Kenya Medical Research Institute said results showing the shot offered 46 percent protection for 15 months meant it had 'promise as a potential public health intervention against childhood malaria in malaria endemic countries'," the news service notes (Kelland, 1/14).

"The findings suggest [GlaxoSmithKline] may have succeeded where others have failed in developing the world's first effective shot against the deadliest mosquito-borne disease," Bloomberg Businessweek writes. "Glaxo expects to have the results of final-stage trials by late this year or early next, Chief Executive Officer Andrew Witty said in October."

"We've never had a malaria vaccine get this far in its development and continue to show such promise," Director of the WHO Global Malaria Program Robert Newman said. "It's promising and encouraging" (Bennett, 1/13).

For the study, between March 2007 and October 2008, researchers randomly assigned 894 children five to 17 months from Kenya and Tanzania to doses of the GlaxoSmithKline vaccine, also known as Mosquirix, or a rabies vaccine, according to a Lancet press release. "Blood samples were taken before vaccination and at regular intervals during the trial to test for antibodies," the release states.

Initial tests of the RTS,S, published in 2008 showed the vaccine provided 53 percent protection against malaria for at least eight months, and scientists were interested if the vaccine provided a similar level of protection after an additional seven months (1/13).

The Telegraph reports: "After 15 months, those who had [received] the malaria vaccine were [45.8] percent less likely to have been infected with the [malaria parasite] P. Falciparum parasite than the control group. Only 11.4 percent of those given the vaccine developed clinical malaria, compared to 19.7 percent of the other group."

The vaccine works by attacking the parasite when it first enters the bloodstream or liver cells, with the aim of completely preventing infection of red blood cells (Adams, 1/14).

"RTS,S/AS01E provides sustained protection from clinical malaria over a period of 15 months (range 12 - 18 months) in young children residing in malaria endemic areas. … Furthermore, we recorded no waning in efficacy during the trial," the authors of the study write (Olotu et al., 1/14).

"The most common adverse events were pneumonia, fits with fevers and stomach inflammation, with fewer events reported among children who received the malaria vaccine compared with those who got the rabies shot," Bloomberg Businessweek adds (1/13).

The study authors also note, "A limitation of our study is that we recruited healthy children only; further studies are needed to establish vaccine efficacy in, for example, children with HIV infection or those who are malnourished. Furthermore, phase 3 studies should include study sites at different transmission intensities to confirm how generalisable our results are" (Olotu et al., 1/14).

"Late-stage trials of the [RTS,S] in 16,000 children in seven countries across Africa are ongoing, with immunisations due to end next month," Reuters writes. "GSK chief executive Andrew Witty has said that if RTS,S proved effective in final-stage trials it would be sold at a price that those who need it most can afford. The company has said it was planning for a profit margin of 5 percent over the cost of making the vaccine, and that would be reinvested in new vaccines for malaria and other neglected diseases," according to the news service (1/14).

"Assuming results of the next trial are positive, Glaxo plans to seek regulatory approval for the shot in Europe, Stephen Rea, a spokesman, said in a telephone interview," Bloomberg Businessweek writes. "The WHO wants to wait for data on the effectiveness of the vaccine after 30 months, due in 2014, before it makes a policy recommendation on the vaccine, Newman said" (1/13).

An accompanying Lancet Infectious Diseases Comment also reflects on the results of the trial (Greenwood, 1/14).