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Two papers have been published in the Lancet and Lancet Infectious Diseases journals: one which presents the results of a phase III clinical trial of a candidate malaria vaccine which the research team report to effective in reducing malaria transmission, and another which has estimated the number of cases of and deaths from malaria in West African countries affected by the current Ebola outbreak.
Prof. Adrian Hill, Director of Jenner Institute, University of Oxford, said:
“This is a huge study* of the first malaria vaccine candidate to reach phase 3 testing and a milestone in the field. The results extend the three previous major papers on this trial with data now on three to four years of follow-up and assessment of a booster dose.
“The authors emphasise that the vaccine can prevent a large number of cases of uncomplicated malaria and suggest that it may be worth deploying in some settings. This is controversial. There was no impact on malaria mortality and no significant effect on severe malaria: non-significant reductions of just 1% and 10% were observed in the children and infants studied over the full trial period using a three dose regimen. This is clearly lower than the efficacy of impregnated bed nets. However, the effect on malaria episodes – convincing reductions of about 25% to 30% – is of interest, even though the episodes prevented are a small fraction of those that did occur in the vaccines.
“Because the vaccine’s efficacy is so short-lived, as expected a booster dose is shown to be of some value but it was not as effective at the initial doses. More worrying is the new evidence of a rebound in malaria susceptibility: after 20 months vaccinated children who were not boosted showed an increased risk of severe malaria over the next 27 months compared to non-vaccinated controls.
“So, overall, this work is a substantial scientific achievement in providing the first vaccine with any efficacy in young children. But its potential public health benefits and utility is not yet clear. It should be possible to make the vaccine more effective in some settings with improved scheduling, but that will probably increase delivery costs substantially. More likely, adding further vaccine antigens in second generation vaccines, now under active development, will address this dilemma.”
Prof. Mike Turner, Head of Infection at the Wellcome Trust, said:
“The RTS,S Clinical Trials Partnership study* represents a milestone in the development of malaria vaccines. It has taken 20 years to get here and, while the levels of protection the vaccine offers against clinical malaria may seem relatively low, they are better than any other potential vaccine we currently have. The findings are not only important in their own right but also in signposting a road to developing better vaccines in the future. We must work towards making it a road that does not take another 20 years to travel.
“Other research published todayǂ, from Patrick Walker and colleagues, provides much needed evidence of the impact of the Ebola epidemic on malaria, as a result of the effects on healthcare systems in West Africa. It highlights the wider consequences of such outbreaks, which are significant not only for diseases like malaria, and HIV, but for vaccination programmes, maternal and child health, and broader healthcare provision. It also demonstrates the very real need to invest in the prevention of and recovery from infectious disease epidemics, in which vaccines have a crucial role to play.”
* ‘Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: final results of a phase 3, individually randomised, controlled trial’ by the RTS,S Clinical Trials Partnership published in the Lancet on Friday 24 April 2015.
ǂ ‘Malaria morbidity and mortality in Ebola-affected countries caused by decreased health-care capacity, and the potential effect of mitigation strategies: a modelling analysis’ by Patrick G T Walker et al. published in Lancet Infectious Diseases on Friday 24 April 2015.
Declared interests
Prof. Adrian Hill is Director of the Jenner Institute at Oxford University which is developing a range of next generation malaria vaccines with support from many non-profit funders. He is collaborating with GSK on various vaccine development programmes.
Prof. Mike Turner: Several members of the RTS,S Clinical Trials Partnership, and authors on that paper, are members of the KEMRI-Wellcome Trust Research Programme.