RTS,S Malaria Vaccine Candidate Shows Moderate Efficacy in Infants

In 2011, the results of a Phase III clinical trial of the RTS,S vaccine candidate in children aged 5 to 17 months showed that three doses of RTS,S reduced the risk of clinical malaria by 56% and of severe malaria by 47%.  New results following the vaccination of infants aged 6 to 12 weeks show the vaccine to be moderately effective, producing a 31% reduction in the risk of malaria in this population. These findings, which have been published online in the New England Journal of Medicine (NEJM), were announced today at the International African Vaccinology Conference (VACFA) in South Africa.

Efficacy and safety was monitored for 12 months in 6.537 infants aged 6 to 12 weeks on enrolment. The RTS,S vaccine was coadministered alongside the vaccines routinely given to infants at 2, 3 and 4 months of age. The trial is ongoing in eleven research centres in seven sub-Saharan African countries, including the Manhiça Health Research Centre in Mozambique.

The Phase III clinical trial of RTS,S began in May 2009 and is scheduled to end in 2014 with the publication of final data on the overall result. Those findings will provide additional information on the duration of the vaccine's efficacy at the different trial sites, and on the factors that may influence the difference in efficacy between older and younger infants. Once the final results are available, the World Health Organisation will evaluate all of the evidence and decide whether to recommend the RTS,S vaccine for use as a malaria control measure.

Fundamental Advance

The results of this Phase III clinical trial of RTS,S represent a fundamental advance in the search for a malaria vaccine that can be used to control this deadly disease. Until the vaccine reaches the market, however, it is essential to continue promoting the use of existing measures, such as impregnated bed nets, intermittent preventive treatment in infants and pregnant women, and appropriate and timely treatment of clinical cases of malaria.  In the last decade, the use of such measures, in conjunction with improved health systems and new drugs, has reduced mortality from malaria by more than 25% worldwide and 33% in Africa.

In Spain, CRESIB, the research arm of ISGlobal, in partnership with the Hospital Clínic of Barcelona and the University of Barcelona, has developed and evaluated several malaria control measures, including insecticide-impregnated mosquito nets and intermittent preventive treatment in infants (IPTi) and pregnant women (IPTp). During the last 12 years, CRESIB has also contributed to the assessment of the RTS,S malaria vaccine candidate, for which it carried out the initial proof-of-concept trials demonstrating the safety and partial efficacy of RTS,S. The results of those trials made possible the current phase III trial, the first of its kind in Africa. CRESIB is now coordinating the immunology studies of RTS,S, which will give us a better understanding of the mechanisms of protection and may open the door to improvements in this and other vaccines.

The RTS,S vaccine candidate was developed by GlaxoSmithKline in collaboration with a number of public and private institutions. Funding for the RTS,S trials has come primarily from a grant made by the Bill & Melinda Gates Foundation to the Malaria Vaccine Initiative (MVI).