09/28/2022 – A new vaccination to the malaria developed by scientists at the University of Oxford was 80% effective in preventing disease in young people childrenaccording to test results published at the beginning of September. DyannWirthRichard Pearson Strong Professor of Infectious Diseases offers some thoughts on the new vaccine and its potential impact.
Q: Media reports have suggested that the new vaccine could be “world-changing.” As someone who has studied malaria for years, are you similarly excited?
A: Whether it will be world-changing remains to be seen, as so far there have only been early tests of its effectiveness.
This new vaccine, called R21, may be an improved version of another vaccine called RTS,S, which the World Health Organization approved last October for widespread use in regions with significant malaria transmission. RTS,S was the very first vaccine against a human parasitic infection.
RTS,S also showed high efficacy in limited samples in early testing, but once deployed in a more real setting – in phase 3 clinical trials – both predicted and observed efficacy declined closer to 40% to 50% they stayed that way. It turns out that how the vaccine is administered relative to the season of transmission affects its effectiveness. In many countries, the spread of malaria is typically highest during the rainy season, when there is more standing water for mosquitoes to breed. A recent study by Brian Greenwood of the London School of Hygiene and Tropical Medicine and colleagues found that an RTS,S vaccine given just before the transmission season in West Africa had extremely high efficacy.
For R21, only 450 children aged 5 to 17 months, a small number, were included in the recent study in Burkina Faso, where malaria infections are seasonal. The study showed that three initial doses of vaccine, followed by a booster dose a year later, were 80% effective in preventing infection.
I would say that we need to evaluate R21 under more realistic conditions, including the phase 3 clinical trial that started in April 2021 and will run until December 2023, involving 4,800 children in four African countries, including two where malaria is a threat during the whole year. I’m optimistic about the new vaccine, but I also recognize that early data is often more promising than when things actually get used in the field.
Q: How important is it to have this new, hopefully effective, vaccine?
A: Total global demand for this vaccine could be up to or over 100 million doses per year. As we now know from the coronavirus experience, having more than one vaccine source is critical to withstand potential supply chain disruptions, quality control issues, or other issues.
After the WHO recommended the widespread use of RTS,S last October, this has led to a paradigm shift in my opinion. There is now significant new effort in developing malaria vaccines. BioNTech, one of the developers of the mRNA-based coronavirus vaccine, wants to develop an mRNA-based vaccine against malaria and there will be clinical trials for it soon. There is also a very large program funded by the Gates Foundation to use monoclonal antibodies as a preventative against malaria. I think all the excitement and development in this area is great considering there are 280 million cases of malaria and almost half a million child deaths every year.
Aside from vaccines, the other two main approaches we have to combat malaria are vector control – which essentially prevents the mosquito from biting humans, either by killing the mosquito or by using insecticide-treated bed nets – and diagnosis and treatment with antimalarial drugs. However, drug resistance is a problem.
There is an enormous need for new approaches to combat malaria, as microorganisms such as the malaria parasite have various ways of avoiding death. Evasion is a common trait. We have seen a similar scenario with the coronavirus, where the variation in the virus has significantly reduced the effectiveness of previous immunity caused by either the vaccine or the disease. I think this also applies to malaria. Data has shown that there is strain-specific protection similar to what we see with the coronavirus. With these struggling microorganisms like the malaria parasite, I think we should be less naïve and believe that there will be a miracle cure. We will continue to need other tools and additional vaccines.
Q: An expert was quoted in the press as saying that the development of the new vaccine indicates that it may be possible to end child deaths from malaria in our lifetime. What do you think?
A: I hope that’s true. This is a preventable, treatable disease. No child should die from this.
The reality is that between about 2005 and 2015, child malaria deaths were halved through better implementation of bed nets, diagnosis and treatment. And then things stagnated. A vaccine that represents an entirely different strategy could have an effect if used skillfully, by vaccinating or boosting just before the rainy season for maximum effect, while also utilizing the other tools in our arsenal. I’m very excited about the potential we could dramatically impact by deploying a multi-pronged strategy.
– Karen Feldscher
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