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How close are we to a vaccine for malaria?

24 Apr, 2015

On the eve of World Malaria Day 2015, the global health community is celebrating the publication of the final data on the efficacy of the world’s most advanced malaria vaccine, RTS,S. Here, Professor Philip Bejon, Director of the Kemri-Wellcome Trust Research Programme in Kenya and an author of today’s Lancet Infectious Diseases paper, describes the 30 year journey scientists have taken to get to this point and his hopes for the malaria vaccines of the future…

Malaria prevalence in Africa, 2000-2010

Despite studying the disease and living in Kenya for some years, I’ve never had malaria.  Some of my colleagues have, and attitudes to catching malaria range from the matter-of-fact through to bravado. The ease with which we can access rapid diagnosis and treatment ensures that, for us, our attitudes don’t include any real fear. For many Kenyan children, who are less able to access care, malaria carries a much greater threat. A conservative estimate is that half a million children in Africa died of malaria last year. There are also well-documented knock-on effects on their nutrition and growth, their school attendance and their family finances as their parents seek treatment.

The global health community is united in its belief that there is a great need not just for better treatments for malaria, but for a preventative malaria vaccine. Today, a large group of scientists including myself have published the results of the largest ever malaria vaccine trial, conducted for the candidate vaccine known as “RTS,S”.  Our data show that the vaccine has some protective efficacy, but is by no means perfect.

There are now complex discussions and analyses to be done by regulators and policy-makers about cost-effectiveness before further decisions on the use of the vaccine are taken.   These decisions will take account of the millions of malaria episodes and deaths each year, the precise degree of efficacy demonstrated, how long protection lasts , data on safety and the cost of the vaccine and of delivering it.

Whatever the outcome of the regulatory and policy discussions, the positive impact of RTS,S on the field of malaria research is still dramatic. RTS,S has been in development for almost 30 years, and the thread of scientific discoveries leading to the development goes back decades further.  During that time there have been many false starts with vaccine candidates that were abandoned, or that were returned to the drawing board for redesigning.  However, we have learnt a lot from this long journey about what is required for a malaria vaccine, and, crucially, that our goal is possible.

B0006056 Mosquito, Anopheles stephensi in flightNow, the key question for researchers and the malaria community is whether we can speed up the process of making the next malaria vaccine. As with all research, increased funding and good collaboration certainly helps. The clinical development of the RTS,S vaccine has been accelerated by many organisations working to support a series of trials in Africa, working in collaboration with investigators based in African countries.

Can we shorten the clinical development?  The latter stages of large-scale testing took 5 years, including follow-up, and it’s hard to see how that could be contracted further.  The earlier phases of testing in smaller groups could perhaps be accelerated, and lessons learnt regarding how to maximize the immune response will stand us in good stead for the future.  We can draw on our partnerships and experience to repeat the process with any new vaccine.

Possibly the best way of accelerating future vaccine development is to understand more of the science leading up to vaccine design.  The guesswork required during the iterative process of vaccine testing in the field can be painfully slow. If we can reduce the guesswork by having more intelligence about the malaria parasite, then we will take fewer “false turns” that take us back to the drawing board.

We need to know more about how antibodies and immunity work, more about how the parasite evolves, and more about the most promising targets of immunity.  At the Kemri-Wellcome Trust programme we are committed to working on the basic science issues as well as the field testing of developing products, and we are joined in this by many other centres across Africa.  Studying natural immunity can give us important clues for the future – not necessarily in attempting to reproduce natural immunity, but in understanding which components of an immune response appear most promising as targets for a vaccine.

We should expect that the current result on RTS,S will have a dramatic and positive impact on the field of malaria vaccine development irrespective of the specific decisions that regulators and policy makers will take after viewing the data.  The results encourage us to believe that it is possible to make malaria vaccines that protect children – something that was by no means clear even 10 years ago.  My hope for the future is that we can encourage the brightest minds, especially among African scientists, to be applied afresh to the basic science of malaria, the technical challenges of vaccine development, and to obtaining the funds necessary to drive it forward at the maximum pace.

For more information about the Kemri-Wellcome Trust Research Programme visit their website, here.

Reference: ‘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. Lancet Infectious Diseases

Images: (Top) Predicted 1 × 1 km spatial resolution Plasmodium falciparum parasite rate endemicity class maps of Africa Credit: Noor et al, in the Lancet(Bottom) Mosquito, Anopheles stephensi in flight Credit: Hugh Sturrock, Wellcome Images.

One Comment leave one →
  1. 4 May, 2015 3:16 am

    What is RTS,S?

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