Malaria vector control guidelines

Over the decades, WHO has produced a large amount of valuable literature on malaria vector control, but it can be very difficult to navigate and to identify which information is the most up-to-date, or how different recommendations and guidance link together.

These guidelines aim to overcome this challenge and simplify life for everyone involved in malaria vector control by creating a “one-stop shop” where all WHO key recommendations in this field are consolidated. And just as importantly, the guidelines are meant to greatly increase the transparency around the level of available evidence on which the WHO guidance is based.

The ultimate goal of these guidelines is to ensure the best use of available resources for malaria vector control founded on a solid evidence base.

Yes, we decided to bring recommendations and good practice statements all together in one document, as these complement each other.

Recommendations are generally based on systematic reviews of evidence generated by randomized controlled trials and other rigorously designed and implemented studies. For example, a considerable number of trials have generated solid evidence that using insecticide-treated nets (ITNs) will reduce malaria in the geographic area where they are deployed. Based on this evidence, ITNs are recommended as a core intervention for malaria control. The recommendations tell people "what to do" – i.e. what intervention works.

The best practice statements are more about "how to"; they are largely based on expert opinion and field experience, as the evidence around them tends to not be generated by randomized trials. Using the example of ITNs, a best practice statement is that users should be educated not to wash their nets in fresh water bodies or use them for fishing as we know that pyrethroids used on the nets are very toxic to aquatic organisms.

By making the recommendations more user-friendly, I think people will be more receptive to using them. I hope the guidelines make it much easier for national malaria control programmes and implementing partners not only to develop evidence-based vector control policies and strategies, but also to understand how specific tools should be deployed according to specific circumstances.

By pulling together the "what to do" and the "how to do it" in one publication, countries will be better able to adapt their efforts to a particular malaria landscape. This will ultimately strengthen the link between the data that countries generate through their own research, including trials, their monitoring and surveillance activities (e.g. of insecticide resistance) and the use of this data in decision-making.

The guidelines are largely a consolidation of existing recommendations as opposed to new ones. However, by bringing together more than 20 individual sets of WHO recommendations into one "go-to" document and combining them with best practice statements, it becomes a lot clearer what the key messages are in malaria vector control and how they all link together.

As part of the guideline development process, the Cochrane Infectious Diseases Group also conducted new systematic reviews or updated existing ones. This has provided the foundation for new – or at least clearer – recommendations. An example of this concerns the use of space spraying of insecticides, where it is made clear in the guidelines that this intervention should not be undertaken for malaria vector control.

There are a number of reasons why there may be insufficient or poor data available on the effectiveness of certain interventions. The limited number of trials on IRS, and hence the weak evidence base for this intervention, provides a good example. Here we are dealing with an intervention that was first introduced over 50 years ago, at a time when the process to develop WHO recommendations and the associated evidence requirements had not been defined.

Subsequently, a lot of operational experience has been gained that supports the use of this intervention, but randomized controlled trials aimed at generating gold standard evidence to establish the efficacy of this intervention are few and far between. In such cases, the development of WHO guidance relies to a considerable extent on lower quality evidence and expert opinion. In the formulation of recommendations, experts will also consider several factors other than data-based trials and studies, including:

• balance of benefit and harm;
• the values and preferences of individuals and populations affected by the recommendation (i.e. what importance people assign to the outcomes associated with the intervention);
• the acceptability of the intervention to the most important stakeholders, as well as feasibility and resource implications.

Absolutely. I believe the new document helps increase the level of transparency around the evidence that underpins WHO recommendations, and hence on the process that needs to be followed to generate an evidence base that allows WHO to develop or revise recommendations on vector control.

Through greater transparency, we hope that innovators and research partners will understand why new tools and interventions need to be fully evaluated. After all, in the resource-constrained environment that most malaria-endemic countries operate in, the choice of a vector control intervention will come at the cost of something else, so prioritizing one over the other needs to be well justified. We really want all malaria stakeholders to recognize the benefits of conducting solid research which, in turn, generates an evidence base from which WHO can develop recommendations.

In addition, the intensive process of putting together a comprehensive evidence base for these guidelines has helped to identify where there are evidence gaps, and this will help to inform the research agenda for the ongoing development of the guidelines.

We see the Guidelines for malaria vector control as a "living document". They are very much a work in progress and will continually take into account new tools, new evidence, and new guidance. We plan to update the guidelines on an ongoing basis; the document will only be made available in a web-based format so that it can be revised as soon as new evidence is assessed by WHO.

In parallel, we aim to continue improving and clarifying how new tools are evaluated, and we will continue to look for opportunities to make the evaluation process more nimble. We are also seeking input from people using the guidelines. We really want to emphasize that in order for these guidelines to be as good as possible, we do need to have people’s feedback and willingness to contribute towards them.

For this purpose, we have set up a dedicated email address to which feedback can be directed:vcguidelines@who.int. We will also be proactively collecting user feedback through other means, including regular user surveys.