New malaria vaccine reaches 75% efficacy

An Oxford team are behind this malaria treatment - the first to meet a crucial WHO target...
04 May 2021

Interview with 

Katie Ewer, University of Oxford

MOSQUITO_ON_SKIN

Female Aedes albopictus mosquito on skin

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Scientists from the University of Oxford have produced a new malaria vaccine that, they say, is more than 75% effective - making them the first to meet a crucial target set by the World Health Organisation. They’ve just completed their Phase II trials in West Africa, where they were able to reduce malaria infections in a group of children by three quarters. Chris Smith heard from immunologist Katie Ewer…

Katie - Yes, it's a great achievement. We've been working towards this for quite a long time now, so to finally have this result after so long and so many different vaccines that we've tested in clinical trials... it's great.

Chris - How does the vaccine work?

Katie - The vaccine primes your immune system to make antibodies against one of the main proteins on the surface of the malaria parasite, so that when you get bitten by a mosquito that's carrying malaria, those antibodies bind up those parasites and stop them from setting up an infection in your body.

Chris - People have been trying to do this for a long time though, haven't they? We've seen many, many trials of malaria vaccines - they don't seem to have been very successful. So why have you managed to triumph where they haven't?

Katie - Malaria is a really complicated infection to make a vaccine against. It has a life cycle in both the human and the mosquito host. And so depending on which part of the lifecycle you want to target, you might need a different type of immune response. So when you make a vaccine against a simple virus, you've only got seven genes to choose from; malaria has around 5000, so just deciding which part of the parasite you want to use as a target for your vaccine is a huge job. The part of the lifecycle that we target with our vaccine takes place just after you get bitten by that mosquito that's carrying the malaria parasite. And we're trying to capture that window - with an immune response - between those parasites going into your skin, and getting to your liver. And that window is only about half an hour to two hours. So it's not long for the vaccine to act to block that infection.

Chris - Ashish, from a public health point of view this must be music to your ears, because malaria is one of the leading causes of death worldwide, isn't it?

Ashish - Oh, this is extraordinary. And we're all going to hope that more data come in supporting this. Over the years, I have always said that if we got a vaccine that was 30-40% effective, we would be thrilled, it would make an enormous difference. So a potential vaccine of 75%... and most of the people who die of malaria are children, so it's particularly an awful disease. And while we've made progress globally, it still kills hundreds of thousands of people every year. So this is extraordinary. I'm trying not to get overly enthusiastic, because we want to see bigger trial data, but everything I've seen so far makes me very, very hopeful.

Chris - Taking that point forward, Katie - because so many victims are children, when is the best time to intervene? Do you intervene in pregnancy so that young newborns don't catch it? Because that's a big issue with malaria, isn't it, when you get a newborn or a young kiddie who catches it and then they don't fight it off as effectively as an adult, and they often become victims.

Katie - Yeah, that's right. And as we just heard, most children who die of malaria are under the age of five in sub-Saharan Africa. So the plan really, because malaria is predominantly a seasonal infection, is to give those children immunity before the start of the malaria season so they have lots of antibodies ready for when those parasites and mosquitoes start biting. So we're looking at vaccinating children in their first year of life before the malaria season starts, and then giving them booster doses every year to top up those antibody levels, before they're exposed to that during the malaria season going forward.

Chris - Is this the sort of vaccine that's pretty stable? Because obviously it's easy to make a vaccine which when you have the perfect environment, such as a laboratory, you can keep fresh; but when you take it out into the back of beyond, where there is no electricity supply, there is no fridge, it's a different story. What's the vaccine construct, as it were?

Katie - Yep, that's a really important point. And people who work on malaria vaccines know that there's no point in making a very expensive vaccine that you have to store in a freezer. It's got to be cheap, it's got to be able to survive a very rural cold chain, and we've got to be able to make hundreds of millions of doses of it. So this is a protein and adjuvant type vaccine - not new technology. It's administered in three doses, as I mentioned. So we really do think that this is feasible to deploy on the scale that's going to be required to really have an impact.

Chris - Next step will presumably be a much bigger trial to then prove it works, it's safe, and really, how effective it can be?

Katie - Exactly. So the data so far is from a phase II trial which was in 450 children in West Africa. We now have approval to start a phase III trial, and that will be in four countries in both East and West Africa, so different levels of malaria transmission intensity; and that will be in 4,800 children. So a much bigger sample size to really, really check for safety and protection in different communities and different populations.

Chris - And of course, one of the most successful - Anna - interventions against malaria hitherto has been the bed net. And that wouldn't exist without a materials scientist!

Anna - Yeah, absolutely. And in the 20th century, it was really a triumph of material science that we were able to mimic the natural plastics that we had - which was things like natural rubber - to make very cheap, easy to produce plastic textiles. And these have then obviously gone on to form our clothes, and all sorts of different textiles in our homes, but also to make nets that will protect against diseases like this.

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