Valuing Data: The Role of Satellite Data in Halting the Transmission of Polio in Nigeria
By Mariel Borowitz, Janet Zhou, Krystal Azelton & Isabelle-Yara Nassar
Publisher’s Note: This blog discusses research published in Data & Policy earlier this year that examined the value of satellite data in halting transmission of polio in Nigeria
There are more than 1,000 satellites in orbit right now collecting data about what’s happening on the Earth. These include government and commercial satellites that can improve our understanding of climate change; monitor droughts, floods, and forest fires; examine global agricultural output; identify productive locations for fishing or mining; and many other purposes. We know the data provided by these satellites is important, yet it is very difficult to determine the exact value that each of these systems provides. However, with only a vague sense of “value,” it is hard for policymakers to ensure they are making the right investments in Earth observing satellites.
NASA’s Consortium for the Valuation of Applications Benefits Linked with Earth Science (VALUABLES), carried out in collaboration with Resources for the Future, aimed to address this by analyzing specific use cases of satellite data to determine their monetary value. VALUABLES proposed a “value of information” approach focusing on cases in which satellite data informed a specific decision. Researchers could then compare the outcome of that decision with what would have occurredif no satellite data had been available. Our project, which was funded under the VALUABLES program, examined how satellite data contributed to efforts to halt the transmission of Polio in Nigeria.
In the 1980s, Polio was rampant around the world, crippling an estimated 350,000 children per year. A global effort to eradicate Polio through the use of widespread vaccination campaigns, beginning in 1988, made impressive progress. Today, all but two countries — Afghanistan, and Pakistan — are Polio-free. The most recent nation to achieve Polio-free status is Nigeria, which was declared Polio-free in 2020. This is impressive, because in 2012, Nigeria accounted for more than half of all cases worldwide. One of the key elements of the recent success in Nigeria involved the use of satellite data.
Satellite data may not be the most obvious tool to turn to when fighting a disease like Polio, but in this case, the information provided by satellites enabled three key improvements. First, researchers at the Oak Ridge National Laboratory, the Bill & Melinda Gates Foundation and elsewhere used satellite imagery, combined with machine learning techniques, to develop a more accurate estimate of the population in Nigeria. They found that the population was larger than traditional estimates had suggested, meaning that the number of individuals that needed to be vaccinated in order to achieve population immunity was higher than vaccination planners had assumed.
Second, researchers from the Nigerian Ministry of Health, the World Health Organization, and the Bill & Melinda Gates Foundation used satellite imagery to create accurate, georeferenced maps. These replaced hand-drawn maps that had previously been used to guide vaccination teams. The satellite-based maps showed that the hand-drawn maps had numerous inaccuracies — in some cases missing entire settlements. If vaccination teams consistently missed whole communities, it would likely have been impossible to reach population immunity, even if other communities reached very high vaccination levels.
Finally, vaccination campaign planners also made use of the maps to enable GPS-tracking of individual vaccination teams. This enabled the teams to review their progress each day, making sure they had not missed any settlements. Settlements that were missed could be visited on a subsequent day. This system, combined with the improved accuracies of the satellite data-based maps, ensured much more complete and consistent coverage during vaccination campaigns.
Within one year of putting in place these interventions across key states, Nigeria halted the transmission of Polio.
All of this occurred years before our research project began — and the impressive success is due to other researchers, experts, and officials working on the program. Our project aimed to take this important and innovative application of satellite data and determine — in monetary terms — how much value it had generated. (Of course, we acknowledge that many benefits — including lives saved and children spared from permanent disability — cannot be fully captured in a dollar value. Still, as discussed above, we believe that valuation can play an important role in supporting good decision-making.)
To determine this value, we considered the costs of developing the satellite information products, as well as the total economic benefits associated with the program. The cost of the satellite data, which was purchased from the commercial remote sensing satellite company, Digital Globe (now Maxar) was approximately $1.5 million. The Gates Foundation invested another $4.25 million to support the research and development necessary to develop and validate the machine learning techniques used to generate population estimates and maps.
In determining the total economic benefits, we limited our analysis to just one year. This conservative approach allowed for the possibility that had transmission continued after 2014, planners would have made other adjustments to the program to move toward halting transmission. (And in fact, there were additional wild Polio cases discovered in 2016, although these were associated with areas inaccessible to vaccinators due to ongoing violence.) Economic benefits included the decrease in the number of children that became ill with the disease, which was translated into a dollar value using disability-adjusted-life-years. We estimated a reduction of between 6 and 122 cases over one year, which translates to between $162,000 and $3,294,000 in value. These numbers are relatively low, since Polio cases tend to be relatively rare in the years leading up to a halt in transmission.
Additional benefits derived from savings associated with the ability to ramp down vaccination campaign efforts. Vaccination campaigns are complex and expensive. They include costs associated with planning, operations, surveillance, and certification. During the campaigns themselves, which typically span 4 to 5 days, teams of vaccinators aim to give two drops of oral polio vaccine to every child under 5 residing in the target area. Campaigns also involve social mobilization and communication to ensure there are high levels of awareness and demand among target communities. Based on reports available from the Global Polio Eradication Campaign, we estimated the total cost savings in this category to be $170.85 million.
In addition to determining these benefits, we also estimated the possibility that transmission of Polio would have been halted, even without the use of satellite data. Although unlikely, this could occur because vaccinators are always striving for 100% vaccination coverage of the population, even though experts estimate that only 80% coverage is required to halt transmission. Furthermore, satellite estimates of population size are probabilistic, meaning that there is some uncertainty regarding the true size of the population. We found that the use of satellite data increased the likelihood of halting transmission in the range of 30% to 91%. This means that the total socioeconomic benefit associated with the use of satellite data was between $51.7 million and $159.7 million.
We believe that this estimate is conservative. Given the importance of satellite-based maps in identifying previously-missed populations, it seems unlikely transmission would have been halted just one year later if satellite data was not available. Some experts even voiced concern that a failure to halt transmission during this period could have led the country to abandon the effort overall. That said, we acknowledge that the use of satellite data was not the only intervention made, nor the only one needed. The use of satellite-data coincided with high-level political support, significant funding and logistical support from national and international organizations, broad support among community leaders, significant resources, and innovative approaches to reaching children in insecure areas.
It is also worth noting that the investments in the data and methodology for creating satellite products to aid in polio vaccination efforts have also been leveraged for other purposes. The Nigerian government now manages a national database originally developed through this program. In addition, the Geo-Referenced Infrastructure and Demographic Data for Development (GRID3) organization arose from these efforts and continues to work with governments in Nigeria and elsewhere to leverage geospatial data to address societal issues.
This case study focuses on just one instance in which satellite data and products played an important role, and it provides just one piece of the puzzle to understanding the value of Earth observing satellites and guiding better decision-making. We hope that further research can continue to add to our understanding of this issue. Further, we hope that sharing information about this case with a broader community can help lead to further collaborations between the satellite and global health communities and generate further tangible improvements in the lives of people around the world.
About the authors
Mariel Borowitz is an Associate Professor in the Sam Nunn School of International Affairs at the Georgia Institute of Technology and head of the Nunn School Program on International Affairs, Science, and Technology.
Janet Zhou is Director, Strategy and Interim Director, Digital Connectivity at the Bill & Melinda Gates Foundation.
Krystal Azelton is Director of Space Applications Programs at the Secure World Foundation.
Isabelle-Yara Nassar is a Graduate in International Affairs from the Georgia Institute of Technology, where she studied with a focus in global economic development.
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This is the blog for Data & Policy (cambridge.org/dap), a peer-reviewed open access journal exploring the interface of data science and governance. Read on for five ways to contribute to Data & Policy.
