Maarten Voors

Objectives: Most low-income countries are characterized by poor health infrastructures and lack systems needed to timely detect and control disease outbreaks, such as the 2014-16 Ebola Viral Disease and COVID-19. In such contexts, a “One Health” approach, which involves investing in both human and animal health systems, plausibly improves local health outcomes by enabling early detection of zoonotic diseases before they are transmitted to humans, and by timely triggering a health system response needed to mitigate possible outbreaks. There is an urgent call to translate One Health into action and create inclusive and sustainable policies. There is, however, little direct evidence on the gains from One Health approaches. We contribute here by using a randomised intervention to assess the impact of a participatory community-based One Health program. Evidence before this study: A 2016 systematic review searched Scopus, PubMed, and ISI Web of Science using the term “One Health”, restricting publication date between 2003 and 2015.1 The search yielded 1,839 unique articles, but only four evaluated a One Health intervention using quantitative metrics. We performed the same search on 10 April 2023. Reflecting the burgeoning interest in One Health, we found an additional 9,715 unique articles. In total, only 17 articles, however, evaluated a One Health intervention implemented in real-world settings, utilizing quantitative metrics. Furthermore, these studies did not employ experimental methods to assess impact, relied on datasets with often only few observations, and focused exclusively on disease incidence. In the Supplementary Material (Appendix A), we provide a flowchart of the literature review and summarize these 17 related studies. Contribution: This study is the first cluster-randomised trial to assess the impact of a participatory community-based intervention establishing local health platforms employing a One Health approach. We evaluate the intervention at scale and explore the impact of the program on human health, but also on key intermediary outcomes like animal health and animal and human health behaviours. Design: Cluster-randomised control trial. Setting: 363 villages in rural Sierra Leone Participants: The Sierra Leone government and communities recruited, trained and installed Community Animal Health Workers (CAHWs) to work alongside Community Health Workers (CHWs) in 300 randomly selected rural villages in Sierra Leone. Another 63 villages were randomly selected as control sites and had CHWs exclusively. CAHWs provided essential animal health services, disseminated information regarding animal and human health best practices, and actively participated in surveillance efforts by reporting suspected disease symptoms to government supervisors. Main outcome measures: Survey based measures of human health, as well as key intermediary outcomes; including animal health, animal and human health-related behaviours, integration into public services, and household wealth. Results: In July and August 2017, the community-based One Health program successfully recruited, trained and installed CAHWs across 287 villages. Throughout the program's duration, spanning from July 2017 to July 2019, the CAHWs reported on 19,283 suspected disease-related events. Using survey data from over 2,500 respondents, collected in March and April 2020, we found no evidence for impacts on human health (-0.008 Standard Deviation Units (SDU), 95% CI -0.148, 0.133). The program did however significantly improve core intermediary outcomes, including animal health (0.164 SDU, 95% CI 0.017, 0.311), animal husbandry practices (0.255 SDU, 95% CI 0.087, 0.424), human health behaviours (0.187 SDU, 95% CI 0.025, 0.348), integration into public services (0.339 SDU, 95% CI 0.137, 0.541), and household wealth (0.163 SDU, 95% CI 0.053, 0.273). Conclusions: Participatory community-based One Health interventions can serve as a guide for policymakers that seek to strengthen the national health systems by improving disease surveillance and preventative practices that are expected to increase health security nationally and globally. More research is needed to understand how the magnitude, modality, and timing of the program and background conditions may shape program impact on human health. Trial registration: The trial was registered at the National Trail Registry (#21660), which is part of the ICTRP, and OSF (https://osf.io/9xfv3).

Less than 30% of people in Africa received a dose of the COVID-19 vaccine even 18 months after vaccine development¹. Here, motivated by the observation that residents of remote, rural areas of Sierra Leone faced severe access difficulties², we conducted an intervention with last-mile delivery of doses and health professionals to the most inaccessible areas, along with community mobilization. A cluster randomized controlled trial in 150 communities showed that this intervention with mobile vaccination teams increased the immunization rate by about 26 percentage points within 48–72 h. Moreover, auxiliary populations visited our community vaccination points, which more than doubled the number of inoculations administered. The additional people vaccinated per intervention site translated to an implementation cost of US $33 per person vaccinated. Transportation to reach remote villages accounted for a large share of total intervention costs. Therefore, bundling multiple maternal and child health interventions in the same visit would further reduce costs per person treated. Current research on vaccine delivery maintains a large focus on individual behavioural issues such as hesitancy. Our study demonstrates that prioritizing mobile services to overcome access difficulties faced by remote populations in developing countries can generate increased returns in terms of uptake of health services³.

Carbon offsets from the REDD+ (reducing emissions from deforestation and degradation) framework to protect forests are expected to see a 100-fold increase in market value by 2050. However, independent causal impact evaluations are scarce and only a few studies assess benefits to communities themselves, a core objective of REDD+. Following a pre-analysis plan, we use a before-after-control-intervention (BACI) framework to evaluate the impact of a large-scale voluntary REDD+ project in Sierra Leone—the Gola project. We use a panel of both satellite images and household surveys to provide causal evidence of the impact of the project on local deforestation rates and socioeconomic indicators over the first 5 yr of its implementation. We find that REDD+ slowed deforestation by 30% relative to control communities while not changing economic wellbeing and conservation attitudes. We find suggestive evidence that the programme increased the value of alternative income sources, by shifting labour away from forest-dependent farming activities. A cost-to-carbon calculation shows that REDD+ led to 340,000 tCO₂ in avoided emissions per year, with an estimated cost of US$1.12 per averted tCO₂. Our study contributes to developing an evidence base for voluntary REDD+ projects and offers a robust approach to carry out BACI assessments.

Background: The Coronavirus Disease 2019 (COVID-19) pandemic and associated mitigation policies created a global economic and health crisis of unprecedented depth and scale, raising the estimated prevalence of depression by more than a quarter in high-income countries. Low- and middle-income countries (LMICs) suffered the negative effects on living standards the most severely. However, the consequences of the pandemic for mental health in LMICs have received less attention. Therefore, this study assesses the association between the COVID-19 crisis and mental health in 8 LMICs. Methods and findings: We conducted a prospective cohort study to examine the correlation between the COVID-19 pandemic and mental health in 10 populations from 8 LMICs in Asia, Africa, and South America. The analysis included 21,162 individuals (mean age 38.01 years, 64% female) who were interviewed at least once pre- as well as post-pandemic. The total number of survey waves ranged from 2 to 17 (mean 7.1). Our individual-level primary outcome measure was based on validated screening tools for depression and a weighted index of depression questions, dependent on the sample. Sample-specific estimates and 95% confidence intervals (CIs) for the association between COVID-19 periods and mental health were estimated using linear regressions with individual fixed effects, controlling for independent time trends and seasonal variation in mental health where possible. In addition, a regression discontinuity design was used for the samples with multiple surveys conducted just before and after the onset of the pandemic. We aggregated sample-specific coefficients using a random-effects model, distinguishing between estimates for the short (0 to 4 months) and longer term (4+ months). The random-effects aggregation showed that depression symptoms are associated with a increase by 0.29 standard deviations (SDs) (95% CI [−.47, −.11], p-value = 0.002) in the 4 months following the onset of the pandemic. This change was equivalent to moving from the 50th to the 63rd percentile in our median sample. Although aggregate depression is correlated with a decline to 0.21 SD (95% CI [−0.07, −.34], p-value = 0.003) in the period thereafter, the average recovery of 0.07 SD (95% CI [−0.09, .22], p-value = 0.41) was not statistically significant. The observed trends were consistent across countries and robust to alternative specifications. Two limitations of our study are that not all samples are representative of the national population, and the mental health measures differ across samples. Conclusions: Controlling for seasonality, we documented a large, significant, negative association of the pandemic on mental health, especially during the early months of lockdown. The magnitude is comparable (but opposite) to the effects of cash transfers and multifaceted antipoverty programs on mental health in LMICs. Absent policy interventions, the pandemic could be associated with a lasting legacy of depression, particularly in settings with limited mental health support services, such as in many LMICs. We also demonstrated that mental health fluctuates with agricultural crop cycles, deteriorating during “lean”, pre-harvest periods and recovering thereafter. Ignoring such seasonal variations in mental health may lead to unreliable inferences about the association between the pandemic and mental health.

Useful and reliable impact evaluations: Where do opportunities to study the impact of development interventions arise?: Studying the impact of development interventions is not straightforward. Simple comparisons fall short, because differences in, for example, poverty are often not due to just the intervention, but also to other factors. In this article, we discuss examples of projects that studied the impact of interventions in a meaningful and reliable way. We then discuss some practical challenges. We call for a critical approach to impact evaluation designs and for a joint search for opportunities to evaluate impact in a meaningful and reliable way.

In the first six months of COVID-19 vaccine distribution, over 90% of all doses were given to residents of high and upper middle income nations. Less than 30% of Africans were vaccinated with at least one shot even 18 months after vaccine development. This has led to an explosion of scholarly and policy interest on vaccine hesitancy and ways to overcome it. We argue instead that the limiting factor for many rural Africans is lack of access, and implemented an intervention designed to overcome the logistical challenges of last-mile delivery. The cluster randomized controlled trial in 150 remote rural communities shows that simply bringing vaccines to villages using mobile vaccination teams increases the community vaccination rate by 20 percentage points within just 48-72 hours. Moreover, auxiliary populations showed up at our temporary clinic to get vaccinated, which lowers the cost of this intervention to US$ 32 per person vaccinated. This is more cost-effective than most vaccination strategies investigated via trials.