Hi Ian, thanks for sharing this article – our team wrote up some notes on how this topic intersects with our work, and I (Isabel Arjmand writing on behalf of GiveWell) thought it might be useful to share here.
Like the Bloomberg editorial board, we’re concerned about stalling progress in the fight against malaria, but we’re skeptical that quality issues with PermaNet 2.0s have influenced this progress as much as the article suggests.
All things considered, we believe that malaria nets are, and have been, highly effective in reducing malaria burden. The Against Malaria Foundation had first shared the studies highlighted above with us in 2020, and the claims in the Bloomberg article have prompted us to do some additional research.
Based on the work we’ve done so far, we aren’t convinced that decreased net quality is primarily responsible for malaria resurging in Papua New Guinea. So far, we see this as a milder negative update on nets than the article would indicate, in part because we think these tests of net quality may not be a perfect proxy for effectiveness in reducing cases and in part because we no longer fund PermaNet 2.0s (for unrelated reasons). At the same time, renewed interest in the evidence around PermaNet 2.0 quality is a nudge for us to prioritize further work to understand net quality control in general.
More detail on the implications of this research for GiveWell’s work
While we no longer fund PermaNet 2.0s because we now fund newer types of nets instead, they make up roughly 20% of nets we’ve funded historically. The studies referenced in the Bloomberg article looked at nets distributed in Papua New Guinea and indicate that the post-2012 PermaNet 2.0s perform worse on certain efficacy tests. We aren’t sure how well those efficacy tests serve as a proxy for malaria transmission (e.g. mosquitoes in these tests could be impaired from the exposure to insecticides even if it isn’t sufficient to kill them). We’re also skeptical that changes to the formulation of PermaNet 2.0s were the key driver of increased malaria cases in Papua New Guinea. During this time, we think other factors like insecticide resistance and shifts in biting patterns likely played a meaningful role (as highlighted in this paper). That said, we see these studies as a negative update on the effectiveness of those nets.
We did a quick back-of-the-envelope calculation (so this is more illustrative than fully baked, at this point):
Assuming the insecticide treatment on PermaNet 2.0s was 80% less effective after 2012 would make those nets look 30-50% less effective overall than we’d previously modeled. That’s because we model roughly 30% of the benefit of nets as coming from the physical barrier in the absence of insecticide resistance, and we already discount the effectiveness of nets like PermaNet 2.0 because of insecticide resistance. We would guess that with further work, we’d estimate that 80% is on the pessimistic side of things (which would put the overall impact on net efficacy at the low end of our 30-50% range, or lower).
Then, assuming that similar issues don’t apply to other nets (which could be wrong – we plan to look into this more), our overall nets grantmaking would look roughly 5-10% less cost-effective than we’d previously estimated, since PermaNet 2.0s are around 20% of our historical nets distributed. That proportion has varied over time. In 2018, all of the nets we funded were PermaNet 2.0s; now, we fund newer types of nets instead.
While concerns specific to PermaNet 2.0s don’t directly affect our future allocation decisions, this issue does raise more general concerns about quality control for nets. Ideally, we would have prioritized more work in this area in the past. We’re planning to learn more about quality control processes and we also want to better understand how others in the malaria field are thinking about this.
We want to share a few thoughts that might help clarify our approach.
Our research incorporates potential downsides or unintended consequences, such that our recommendations take into account factors like potential side effects. Most (if not all) of the information in Leif Wenar’s WIRED piece is something that anyone could find on our website. However, we believe some of what is published in the piece is misleading or inaccurate. Here is a lightly edited version of the material that GiveWell sent to WIRED in response to a request for comment on Leif Wenar’s piece.