Worldwide, an estimated 172 million people are affected by armed conflict,1 including 59 million people who are forcefully displaced from their homes as internally displaced persons (IDPs) within their countries or refugees who have crossed an international border. This number is the highest forcibly displaced since World War 2. Additionally, natural disasters affect around 175 million people annually.2 The health effects for these populations can be enormous. Good information is essential to understand these impacts and inform effective and accountable humanitarian responses. This Lancet Series on health in humanitarian crises seeks to highlight gaps in our understanding of health responses in humanitarian crises and to discuss ways in improving these responses. This Series focuses particularly on the use of health data, and in this paper, the first in the Series, we examine the evidence base for health interventions in humanitarian crises.
Despite epidemiological studies done on humanitarian crises over the past half century,3, 4, 5, 6, 7, 8 a high degree of concern remains over the quality of data for humanitarian crises,9, 10, 11, 12, 13, 14 how it has been used to guide humanitarian health interventions, and ultimately how effectively humanitarian relief programmes have improved health outcomes.5, 15, 16, 17, 18 This reflects broader demands for greater accountability in the humanitarian sector, which includes strengthening evidence-based decision making to improve the effectiveness of humanitarian responses.19, 20, 21, 22
In this paper, we describe the findings from a systematic review with the aim of examining the overall quantity and quality of evidence on public health interventions in humanitarian crises and identifying the key research gaps. Previous systematic reviews have been done on specific health topics in humanitarian crises, which have provided valuable guidance on the effectiveness of interventions for individual health topics such as mental health and psychosocial support (MHPSS), nutrition, and water, sanitation, and hygiene (WASH).23, 24, 25, 26, 27, 28, 29, 30, 31, 32 However, these topics commonly focused on specific interventions and outcomes. A more comprehensive examination across the range of key health topics could help to identify key research gaps across the humanitarian health sector and guide decision-making on health interventions and research.
The panel presents the methods used for the systematic review. The actual effectiveness of health interventions was not assessed in view of the wide range of health outcomes and interventions and the main focus of the review was on the overall quantity, quality, and the gaps in the evidence. Instead, we present a descriptive summary of the key findings related to the major gaps in the evidence, the strengths and quality of the evidence, and then discuss potential explanations for these findings and how to move forward.
Key messages
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Evidence is important to guide more effective and efficient health responses in humanitarian contexts.
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On the basis of our systematic review, we found that evidence is limited both in quantity and quality.
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Most studies are able to show changes in health outcomes, but most are unable to attribute these changes to the intervention because of the study design used. Where logistically and ethically possible, greater use of experimental and quasi-experimental study designs is needed.
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The findings support calls to scale up quality health research in humanitarian crises.
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Development of innovative integrated funding mechanisms to enable the combination of research projects with humanitarian assistance and create a global humanitarian evidence platform where data and evidence can be accessible to all communities (national authorities, donors, academics, and humanitarian agencies) are needed.