19 October 2011

Time to Start Thinking About the Consequences of a Breathrough on Malaria

The New England Journal of Medicine has released the preliminary results of a field test of a new malaria vaccine by GlaxoSmithKline. An editorial that accompanies the study explains its significance and the author of that editorial notes the unusual step of publishing results beofre the study is actually completed:
It's been a long time coming, and indeed we are still not there yet, but it is becoming increasingly clear that we really do have the first effective vaccine against a parasitic disease in humans. . . It is not usual practice to publish the results of trials in pieces, and there does not seem to be a clear scientific reason why this trial has been reported with less than half the efficacy results available.
It appears that the NEJM timed released to coincide with a major meeting of the Gates Foundation on malaria. The hyping of research results cannot be considered good practice. In the study itself concerns are expressed about side effects, such as an apparent increase in meningitis and seizures.

With these cautions in mind, the implications are potentially huge -- most significantly for improving the lives of Africans who live under the burden of the disease. Here is what I wrote in 2008:
Why does malaria matter? According to Jeffrey Sachs:
The numbers are staggering: there are 300 to 500 million clinical cases every year, and between one and three million deaths, mostly of children, are attributable to this disease. Every 40 seconds a child dies of malaria, resulting in a daily loss of more than 2,000 young lives worldwide. These estimates render malaria the pre-eminent tropical parasitic disease and one of the top three killers among communicable diseases.
The Economist reported a few weeks ago on efforts to eradicate malaria. The article referenced a study by McKinsey and Co. on the “business case” (PDF) for eradicating malaria. Here are the reported 5-year benefits:
• Save 3.5 million lives
• Prevent 672 million malaria cases
• Free up 427,000 hospital beds in sub-Saharan Africa
• Generate more than $80 billion in increased GDP for Africa
Clearly, a successful malaria vaccine, even at 50% effectiveness, would have profound and far-reaching consequences for Africa and the broader world.

For example, successful deployment of a vaccine would have large implications for analysts whose work depends upon making assumptions about the future. Consider that the assumptions used to project future emissions of greenhouse gases from Africa generally do not factor in the GDP boosting-potential of malaria vaccines (in the sense that GDP growth is assumed to be at recent levels or lower).  Again from my posting on this topic back in 2008:
Malaria Scenarios.png
So what are the implications of eradicating malaria for future greenhouse gas emissions from Africa?
To answer this question I obtained data on African greenhouse gas emissions from CDIAC, and I subtracted out South Africa, which accounts for a large share of current African emissions. I found that the average annual increase from 1990-2004 was 5.2%, which I will use as a baseline for projecting business-as-usual emissions growth into the future.

The next question is what effect the eradication of malaria might have on African GDP. The McKinsey & Co. report referenced a paper by Gallup and Sachs (2001, link) which speculates (and I think that is a fair characterization) that complete eradication could boost GDP growth by as much as 3% per year. This would take African emissions growth rates to 8.2%, which is still well short of what has been observed in China this decade, and thus not at all unreasonable. So I’ll use this as an upper bound (not as a prediction, to be clear). So if we graph future emissions under my definition of business-as-usual and also the Gallup/Sachs upper bound, we get the following curves to 2050.

The figure shows that by eradicating malaria, it is conceivable that there will be an corresponding increase in annual African emissions of more than 11 GtC above BAU. . .

The implications should be obvious: If a goal of climate policy is simply to “reduce emissions” then this goal clearly conflicts with efforts to eradicate malaria, which will inevitably lead to an increase in emissions. But if the goal is to modernize the global energy system — including the developing the capacity to provide vast quantities of carbon-free energy, then there is no conflict here.
In case you are curious the IPCC SRES assumes future GDP growth rates in Africa (combined with Latin America) of 3.8% to 5.5% per year to 2050.

The consequences of the eradication of malaria should be received as great news, but such a discovery has the potential to send scenario authors back to the drawing board as it could add to existing scenarios as much as 5 Chinas (! in 2011) worth of emissions in 2050.  Even viewing this idealized value as an upper bound, the lesson here is that emissions scenarios have disproportionately large errors on the high side (PDF).  There are no doubt a wide range of similar types of assumptions and scenarios about Africa that will require rethinking (e.g., food production, uurbanization, conflict, etc.).

Eradication of malaria would be a monumental accomplishment with profound consequences for Africa and the world, beyond the obvious benefits to human health. It is not too early to begin to think through what those might be.