Malaria vaccine trials offer hope of tackling major killer
10 December 2008
In two studies published online in the 'New England Journal of Medicine', researchers have shown that the vaccine candidate, known as RTS,S, provides both infants and young children with significant protection against malaria.
Two separate phase II trials - one of which was carried out at the KEMRI-Wellcome Trust programme in Kilifi, Kenya - reaffirmed earlier study results and support the ongoing efforts, pending regulatory approvals, to launch the phase III study of the vaccine candidate across Africa.
In infants, data show for the first time that the vaccine candidate can be administered as part of existing African national immunisation programmes. In children aged 5 to 17 months, the candidate halved the number of serious cases of malaria over an eight-month follow-up period and was shown to have a promising safety profile.
RTS,S/AS, developed by GlaxoSmithKline (GSK) Biologicals, is the leading candidate in a global effort coordinated by the PATH Malaria Vaccine Initiative (MVI) to develop a malaria vaccine. Malaria kills almost one million people each year, most of them infants and young children in Africa, the intended recipients for this vaccine candidate.
"[These] results strongly show that our investments in developing malaria vaccines are beginning to pay dividends," said Christian Loucq, MVI director. "We are closer than ever before to developing a malaria vaccine for children in Africa. History has shown that vaccines are the most powerful tool to control and eliminate infectious diseases. Clearly, the world urgently needs a safe and effective vaccine to win the war against this terrible disease."
One of the trials enrolled 894 children aged 5-17 months old in both Kenya and Tanzania and was designed to evaluate the safety and efficacy of RTS,S, combined with GSK’s proprietary Adjuvant System, coded AS01. The study was a double-blind randomised clinical trial in which children received either three doses of the RTS,S/AS01 vaccine candidate or a rabies vaccine.
It found that the RTS,S/AS01 formulation reduces clinical malaria episodes by 53 per cent for up to an average of eight months. Earlier studies in Mozambique using RTS,S formulated with a different GSK Adjuvant System (AS02) demonstrated 35 per cent efficacy against clinical disease for 18 months among children aged 1-4. Researchers concluded that these study results support the use of RTS,S/AS01 for upcoming phase III trials.
"These findings build a solid case for phase III testing, which the partners in this endeavour are looking forward to starting in the near future," said Philip Bejon of Kenya Medical Research Institute (KEMRI)-Wellcome Collaborative Research Programme and the Centre for Tropical Medicine, University of Oxford, the study’s lead author.
The second study, involving 340 infants under 12 months of age in Tanzania, found that RTS,S, combined with GSK’s proprietary Adjuvant System AS02, when administered with a commonly used childhood vaccine, did not interfere with the protective immune responses to each of the vaccine components. The childhood vaccine included antigens for diphtheria, tetanus, and heamophilus influenzae B (Hib). In countries where a malaria vaccine is needed most, the current immunisation schedule for infants, called the WHO Expanded Program on Immunization (EPI), would provide an optimal delivery platform.
Image: Scientists at work at KEMRI-CGMR-Coast; KEMRI
References
Bejon P et al. Efficacy of RTS,S/AS01E: clinical malaria in 5 to 17 month old children. N Engl J Med 2008;359. DOI: 10.1056/NEJMoa0807381
Abdulla S et al. Safety and immunogenicity of RTS,S/AS02D malaria vaccine in infants. N Engl J Med 2008;359:2533-2544. DOI: 10.1056/NEJMoa0807773