“We’re at a critical point in the fight against malaria”

In the lead-up to World Malaria Day 2022, we spoke with Dr Audrey Lenhart, Chief of the Entomology Branch in the Division of Parasitic Diseases and Malaria at the US Centers for Disease Control and Prevention (CDC) and incoming co-chair of WHO’s Vector Control Advisory Group (VCAG), about where we are in the global fight against malaria, some of the new innovations being developed to help manage the mosquitoes spreading the disease, and the role of VCAG in both expediting and assessing new technologies for WHO. This conversation has been lightly edited for concision and clarity.

Thanks for taking the time to talk today. First, could you tell us a little about your own background in malaria prevention and how you came to be a part of VCAG?

Sure. Before joining VCAG and even CDC, my background was more focused on Aedes aegypti control [the mosquito that transmits arboviral diseases such as Zika, dengue, chikungunya, and yellow fever] and insecticide resistance. Then when I joined CDC about 10 years ago, my work became much more focused on malaria.

I believe I was initially invited to participate in VCAG because I had experience with both Aedes control and malaria vector control, as well as experience in conducting large field trials of vector control tools with both entomological and epidemiological outcomes. That latter experience aligned particularly well with VCAG’s role in providing feedback to applicants on vector control trial design, and specifically around building a strong evidence base for understanding the public health impact of vector control tools.

What is the role of the VCAG in malaria prevention, exactly? Why was it created, how does it work, and what responsibilities does it have?

VCAG was created to provide an independent way to evaluate the public health value of new interventions coming through the pipeline for vector control. This helps WHO provide evidence-based advice to Member States about the potential deployment of these new tools.

To fulfil its charge, VCAG provides feedback and guidance to groups designing and conducting field trials of new innovations, including advice on trial design and generating high-quality results, so WHO has the most robust evidence base possible to inform its recommendations.

I think it’s important to highlight that, while many of the new tools that are coming through the VCAG pipeline are focused on malaria, some are focused on other vector-borne diseases as well, such as the Aedes-borne arboviruses and others.

Can you talk about the role of innovation in vector control today, and some of the new technologies being applied to combat malaria?

We’re really at a critical point in the fight against malaria. Progress has plateaued in recent years and, in some settings at least, it’s becoming clear that the standard vector control tools that we rely on are not going to be sufficient to eliminate the disease. So, novel interventions that address the growing spread of insecticide resistance and more “atypical” malaria vector behaviours are going to be really important to fill vector control gaps and therefore better protect people from the bites of infected mosquitoes.

That said, not all innovation necessarily needs to be technologically sophisticated. There are strategies such as housing design, environmental management, and simply poverty alleviation that have proven in the past to be effective at reducing malaria in many settings as well.

How do new innovations complement existing interventions such as indoor residual spraying (IRS) and nets? What current problems do they solve?

IRS and ITNs [insecticide-treated nets] are very efficient at targeting vectors that bite people inside houses in the middle of the night. That was the predominant scenario for many years and in many places around the world where malaria is a major public health problem.

But, in a certain sense, I think IRS and ITNs are becoming victims of their own success. Their widespread use has led to now-widespread increases in insects’ resistance to the chemicals commonly used in both interventions. They have also allowed mosquitoes that were historically secondary vectors, due to their different biting behaviours, to now become primary vectors, playing a much more important role in malaria transmission.

I think novel chemistries and some non-insecticide-based interventions are going to be vital for effectively controlling those vector populations that have become resistant to the traditional public health insecticides. Some novel tools will be important for targeting different species of mosquitoes that have different biting behaviours as well. Innovations can fill these gaps.

What challenges do new innovations face before they can become a regular part of national and regional malaria control strategies?

First and foremost, we need to be confident they are safe and effective. When malaria control programmes can be confident that a new tool can safely and effectively control malaria, then they can determine its particular applicability in their country’s malaria transmission settings. Of course, acceptability by local populations is another key consideration, and regulatory and cost factors are also very important.

Given all these new frontiers in innovation control, how does VCAG stay abreast of all the new science and technologies involved?

VCAG is comprised of scientists from all over the world who represent a remarkable breadth of expertise. Each member brings their unique set of expertise to the larger group. It’s hugely rewarding to see how those different perspectives complement each other and result in rich exchanges with the groups running vector control trials. That scope of expertise is, I believe, what makes VCAG so unique and so able to stay abreast of the various aspects of new sciences and technologies that could have an impact.

I have to say it’s quite remarkable to get to see the science as it’s developing in real time. It’s a real privilege to provide feedback to the scientists and innovators that are developing and evaluating these tools in real time.

You mentioned progress on malaria had stalled. Can you talk about the impact that more than 2 years of a global pandemic has had on efforts to control malaria?

As I said, progress in the global fight against malaria had plateaued for several years, even before COVID-19. While the effect of the pandemic on malaria trends has not yet been well-qualified, it will be important to understand exactly what those impacts have been and how they can be mitigated.

On the flip side, there may also be new opportunities that can be leveraged for malaria control arising out of the systems and structures that have been put in place because of the pandemic – for example, enhanced community-based surveillance and the systems countries have put in place to monitor COVID transmission and distribute COVID vaccines through community health networks.

I think there’s been a lot of strengthening of community health infrastructure as a result of the pandemic, and malaria programmes could potentially leverage that moving forward. Lab capacity has been improved in many countries because of COVID-19 too, and this increased capability of sequencing technologies and things of that nature could be leveraged for improved malaria surveillance activities as well.

What would you say the world needs to do to get back to the remarkable progress we saw against malaria from 2000–2015?

That’s a really complicated question. I think we’d all like to know the answer to that! The global malaria community did a tremendous job of scaling up proven interventions over a huge portion of malaria-endemic parts of the world in that period. But I think we reached a point where the prevailing combinations of strategies, tools, and funding had reached their maximum impact. Now we’re at a juncture where we need to re-examine these combinations and figure out how to get back on track so that we’re seeing reductions in malaria cases and deaths again.

Are there any new priorities for VCAG that you want to emphasize as incoming co-chair?

I think it’s a very exciting time to be on VCAG, because, for the first time in its existence really, some of these novel tools have completed VCAG review and others are very close to completion, and so these have started moving through the WHO evidence review group and guidelines development processes. I am hopeful that the guidance that was provided through the VCAG process has contributed to developing a very clear and robust evidence base on which WHO can confidently make recommendations.

Moving forward, I hope we as VCAG can continue to improve the efficiency of that process to get more of these tools through the pipeline and provide countries with even more sound evidence on which to base their decisions. I also hope we’re able to encourage greater representation of scientists from malaria-endemic countries on VCAG in the coming years.