Yesim Tozan
Yesim Tozan
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Associate Professor of Global and Environmental Health
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Professional overview
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Dr. Yesim Tozan’s research centers on health decision science and priority setting, and explores the costs and cost-effectiveness of health care interventions using decision analytic models and the issues of health care resource allocation in low- and middle-income countries. Her main focus has been infectious disease prevention and control with an emphasis on dengue and malaria. Dr. Tozan is currently leading a health economics work package in a European Union-funded research project on dengue surveillance and control with field sites in Sri Lanka and Thailand. She is also leading a prospective multi-center study on the cost of dengue illness in international travelers utilizing a network of travel clinics in Europe, the US, the Middle East and Australia. Most recently, she has been working on economic evaluation of artemisinin-based combination therapies for the treatment of uncomplicated childhood malaria using data from multi-site randomized clinical trials in Africa and Asia. Dr. Tozan was a task force associate for the UN Millennium Project’s Task Force on HIV/AIDS, Malaria, Tuberculosis and Access to Essential Medicines and was lead author of the malaria task force report entitled “Coming to grips with malaria in the new millennium.”
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Education
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BS, Environmental Engineering, Istanbul Technical University, TurkeyMS, Environmental Technology, Bogazici University, TurkeyMA, Public Affairs, Princeton University, Princeton, NJPhD, Public Affairs, Princeton University, Princeton, NJ
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Areas of research and study
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Cost EffectivenessCost-effective Health Programs and PoliciesEconomic EvaluationHealth EconomicsInfectious DiseasesPrevention Interventions
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Publications
Publications
A Scalable Approach to Universal School-Based Mental Health Prevention in Low-Income Countries
AbstractHuang, Y., Nakigudde, J., Park, H., Mugisa, E. T., Tussy, C., Kisakye, E. N., Cheng, S., Boyd, M., Kamya, S., Mayatsa, J., Muyomba, D., Sentongo, H., Tozan, Y., Denis, T., & Brotman, L. M. (n.d.).Publication year
2026Journal title
Journal of the American Medical AssociationAbstract~Effectiveness of behavioural tobacco cessation interventions with and without pharmacotherapy among people living with HIV in Viet Nam: a three-arm pragmatic randomised controlled trial
AbstractTozan, Y., Shelley, D., Armstrong-Hough, M., Nguyen, T., Alvarez, G. G., Kapur, R., Shuter, J., Goldsamt, L., Tozan, Y., Van, M. H., Van, V. G., & others. (n.d.).Publication year
2026Journal title
The Lancet Global HealthVolume
14Issue
3Page(s)
e407--e416Abstract~Health Service Delivery During Humanitarian Emergencies: Quantifying the Impact of Forcibly Displaced Populations, Armed Conflict, and Natural Disasters
AbstractHeadley, T., Shay, C. W., & Tozan, Y. (n.d.).Publication year
2026Journal title
Nature CommunicationsAbstract~Integrating smoking cessation into HIV care settings: A systematic review of the evidence on intervention effectiveness and cost-effectiveness
AbstractTozan, Y., Nguyen, V. M., Hoang, T., Svensson, M., Hoang, M. V., & Ng, N. (n.d.).Publication year
2026Journal title
PLOS ONEAbstractOut-of-Pocket Costs of Chikungunya in Travelers: The 2022-2023 Paraguay Outbreak
AbstractTozan, Y., Tozan, Y., Headley, T. Y., Calle-Prieto, F., Ciruelo, D. P., Lloveras, S., Echazarreta, S. E., Camprub’i-Ferrer, D., Gobbi, F. G., Hamer, D. H., Emetulu, H., & others. (n.d.).Publication year
2026Journal title
Journal of Travel MedicinePage(s)
taag019Abstract~Precision in Peril: Why Global Health Needs a Conflict Health Reporting Checklist (CHERC)
AbstractHeadley, T., Shay, C. W., & Tozan, Y. (n.d.).Publication year
2026Journal title
Bulletin of the World Health OrganizationAbstract~Testing the Impact of Family-Based Intervention to Improve Developmental and Health Outcomes for Female Adolescents: Study Protocol for a Cluster-Randomized Clinical Trial in Ghana
AbstractBahar, O., Addo-Lartey, A., Ibrahim, A., Ssewamala, F., Neilands, T., Tozan, Y., Boateng, A., Byansi, W., Dahlen, A., & McKay, M. (n.d.).Publication year
2026Journal title
BMC Public HealthAbstract~The Association of Armed Conflict with Global Measles Cases: A Structural Equation Modeling Analysis of 193 Countries from 2000 to 2023
AbstractHeadley, T., & Tozan, Y. (n.d.).Publication year
2026Journal title
PLOS MedicineAbstract~A cluster-randomized controlled trial of a combination HIV risk reduction and economic empowerment intervention for women engaged in sex work in Uganda
AbstractTozan, Y., Witte, S. S., Ssewamala, F. M., Kiyingi, J., Bellamy, S. L., Yang, L. S., Nabunya, P., Bahar, O. S., Mayo-Wilson, L. J., Tozan, Y., Mwebembezi, A., & others. (n.d.).Publication year
2025Journal title
Journal of the International AIDS SocietyVolume
28Issue
11Page(s)
e70057Abstract~Climate-driven malaria mortality highest among children in malaria-endemic areas of Uganda
AbstractKiragga, A., Otieno, F., Nabukeera, B., Ng’etich, M., Tozan, Y., & Kajungu, D. (n.d.).Publication year
2025Journal title
BMC Public HealthVolume
25Issue
1AbstractMalaria is a major disease in Africa and is among the leading causes of mortality among children. The disease is highly sensitive to climate change. Prior studies have established a link between climatic factors and malaria mortality, but the evidence specifically related to children in sub-Saharan Africa remains inconsistent and requires further investigation. This study examined the impact of climate variables on malaria mortality in the Iganga and Mayuge districts, a malaria-prone area in Uganda. We used weekly malaria mortality data from a population-based cohort in the Iganga Mayuge Health Demographic Surveillance Site (IMHDSS). In this study, we employed a time series model using a distributed lag non-linear approach to assess the association of weekly climatic factors on malaria mortality across all ages, including children under 5 years and children aged between 5 and 14 years. We also conducted a …Cost-Effectiveness of an Economic Empowerment and Family Intervention for School-Going Adolescent Girls in Uganda, 2017-2022
AbstractSsewamala, F., Tozan, Y., Brathwaite, R., Namatovu, P., Bahar, O. S., Nabunya, P., Nartey, P., & Neilands, T. (n.d.).Publication year
2025Journal title
American Journal of Public HealthVolume
115Issue
9AbstractObjectives. To assess the cost-effectiveness of an economic empowerment and family intervention on mental health outcomes among school-going adolescent girls in Uganda from 2017 to 2022.Methods. We randomized adolescent girls aged 14 to 17 years into 3 arms: (1) health and sex education (usual care; n = 408), (2) youth development accounts (YDAs; n = 471), and (3) a combination intervention (YDA plus multiple family group [MFG]; n = 381). We fitted mixed-effects models and estimated intervention costs prospectively using the microcosting approach.Results. The combination intervention had a statistically significant impact on mental health outcomes (depressive symptoms, hopelessness, self-concept) at 12 and 24 months, except self-esteem at 24 months, relative to usual care, with incremental cost‒effectiveness ratios ranging from $51 to $100 per 0.2-SD change at 12 months, and $53 to …Countries' progress towards Global Health Security (GHS) increased health systems resilience during the Coronavirus Disease-19 (COVID-19) pandemic: A difference-in-difference study of 191 countries
AbstractTozan, Y., Headley, T. Y., Kim, S., & Tozan, Y. (n.d.).Publication year
2025Journal title
PLOS global public healthVolume
5Issue
1Page(s)
e0004051AbstractResearch on health systems resilience during the Coronavirus Disease-2019 pandemic frequently used the Global Health Security Index (GHSI), a composite index scoring countries' health security and related capabilities. Conflicting results raised questions regarding the validity of the GHSI as a reliable index. This study attempted to better characterize when and to what extent countries' progress towards Global Health Security (GHS) augments health systems resilience. We used longitudinal data from 191 countries and a difference-in-difference (DiD) causal inference strategy to quantify the effect of countries' GHS capacity as measured by the GHSI on their coverage rates for essential childhood immunizations, a previously established proxy for health systems resilience. Using a sliding scale of cutoff values with step increments of one, we divided countries into treatment and control groups and determined the lowest GHSI score at which a safeguarding effect was observed. All analyses were adjusted for potential confounders. World Bank governance indicators were employed for robustness tests. While countries with overall GHSI scores of 57 and above prevented declines in childhood immunization coverage rates from 2020-2022 (coef: 0.91; 95% CI: 0.41-1.41), this safeguarding effect was strongest in 2021 (coef: 1.23; 95% CI: 0.05-2.41). Coefficient sizes for overall GHSI scores were smaller compared to several GHSI sub-components, including countries' environmental risks (coef: 4.28; 95% CI: 2.56-5.99) and emergency preparedness and response planning (coef: 1.82; 95% CI: 0.54-3.11). Our findings indicate that GHS was positively associated with health systems resilience during the pandemic (2020) and the following two years (2021-2022), that GHS may have had the most significant protective effects in 2021 as compared with 2020 and 2022, and that countries' underlying characteristics, including governance quality, bolstered health systems resilience during the pandemic.Countries’ progress towards Global Health Security (GHS) increased health systems resilience during the Coronavirus Disease-19 (COVID-19) pandemic : A difference-indifference study of 191 countries
AbstractHeadley, T. Y., Kim, S., & Tozan, Y. (n.d.).Publication year
2025Journal title
PLOS Global Public HealthVolume
5Issue
1AbstractResearch on health systems resilience during the Coronavirus Disease-2019 pandemic frequently used the Global Health Security Index (GHSI), a composite index scoring countries’ health security and related capabilities. Conflicting results raised questions regarding the validity of the GHSI as a reliable index. This study attempted to better characterize when and to what extent countries’ progress towards Global Health Security (GHS) augments health systems resilience. We used longitudinal data from 191 countries and a difference-in-difference (DiD) causal inference strategy to quantify the effect of countries’ GHS capacity as measured by the GHSI on their coverage rates for essential childhood immunizations, a previously established proxy for health systems resilience. Using a sliding scale of cutoff values with step increments of one, we divided countries into treatment and control groups and determined the lowest GHSI score at which a safeguarding effect was observed. All analyses were adjusted for potential confounders. World Bank governance indicators were employed for robustness tests. While countries with overall GHSI scores of 57 and above prevented declines in childhood immunization coverage rates from 2020–2022 (coef: 0.91; 95% CI: 0.41–1.41), this safeguarding effect was strongest in 2021 (coef: 1.23; 95% CI: 0.05–2.41). Coefficient sizes for overall GHSI scores were smaller compared to several GHSI sub-components, including countries’ environmental risks (coef: 4.28; 95% CI: 2.56–5.99) and emergency preparedness and response planning (coef: 1.82; 95% CI: 0.54–3.11). Our findings indicate that GHS was positively associated with health systems resilience during the pandemic (2020) and the following two years (2021–2022), that GHS may have had the most significant protective effects in 2021 as compared with 2020 and 2022, and that countries’ underlying characteristics, including governance quality, bolstered health systems resilience during the pandemic.Countries’ progress towards global health security (GHS) increased health systems resilience during the coronavirus disease-19 (COVID-19) pandemic: a difference-in-difference study of 191 countries
AbstractTozan, Y., Headley, T. Y., Kim, S., & Tozan, Y. (n.d.).Publication year
2025Journal title
PLOS Global Public HealthVolume
5Issue
1Page(s)
e0004051Abstract~Cultural adaptation of clinic-based pediatric hiv status disclosure intervention with task shifting in Eastern Uganda
AbstractKirabira, J., Nakigudde, J., Huang, K.-Y., Ashaba, S., Nambuya, H., Tozan, Y., & Yang, L. (n.d.).Publication year
2025Journal title
AIDS Research and TherapyVolume
22Issue
1AbstractBackground: HIV status disclosure remains a major challenge among children living with perinatally acquired HIV with many taking treatment up to adolescence without knowing their serostatus. This non-disclosure is influenced by factors like fear of the negative consequences of disclosure. Since HIV status disclosure has been found to have good effects including improving treatment adherence and better mental health outcomes, there is a need to design interventions aimed at improving disclosure rates among children living with HIV. This study aims at adapting a clinic-based pediatric HIV status disclosure intervention and tasking shifting from healthcare workers to caregiver peer supporters in Eastern Uganda. Methods: The adaptation process involved consultations with caregivers, healthcare workers involved in the care of children living with HIV, researchers in this field, intervention developers, and other experts and stakeholders. This was done through conducting FGDs with HCWs, caregivers, and peer supporters and consultations with researchers in the field of HIV. The original intervention manual was translated to Lusoga which is the commonly spoken dialect in this region. Collected qualitative data were analyzed using an inductive approach to develop themes and subthemes. Written informed consent will be obtained from all participants before participation in the study. Results: A total of 28 participants were involved in the FGDs, while two pediatricians and two HIV researchers/specialists were consulted. Six themes were generated in relation to all suggested changes to the original manual which were related to: (1) sociocultural beliefs/norms/perceptions (5 FGDs), (2) boosting caregiver’s confidence for disclosure (5FGDs), (3) disclosure mode, environment, and person (4 FGDs), (4) health facility/system related changes (3 FGDs), (5) reorganization/paraphrasing (3FGDs) and (6) age appropriateness (2FGDs). Conclusion: This study emphasized that whereas some aspects of intervention can apply to various contexts, there is a need for cross-cultural adaptation of interventions before being implemented in settings where they were not developed.Cultural adaptation of clinic-based pediatric hiv status disclosure intervention with task shifting in Eastern Uganda
AbstractTozan, Y., Kirabira, J., Nakigudde, J., Huang, K.-Y. Y., Ashaba, S., Nambuya, H., Tozan, Y., & Yang, L. H. (n.d.).Publication year
2025Journal title
AIDS research and therapyVolume
22Issue
1Page(s)
48AbstractHIV status disclosure remains a major challenge among children living with perinatally acquired HIV with many taking treatment up to adolescence without knowing their serostatus. This non-disclosure is influenced by factors like fear of the negative consequences of disclosure. Since HIV status disclosure has been found to have good effects including improving treatment adherence and better mental health outcomes, there is a need to design interventions aimed at improving disclosure rates among children living with HIV. This study aims at adapting a clinic-based pediatric HIV status disclosure intervention and tasking shifting from healthcare workers to caregiver peer supporters in Eastern Uganda.Evaluating the effect heterogeneity of malaria camp interventions in hard-to-reach areas of Odisha state, India
AbstractTozan, Y. (n.d.).Publication year
2025Journal title
PLOS OneAbstract~Impact of Food Insecurity on Smoking Cessation--Related Factors of Tobacco Dependence and Readiness to Quit Among HIV+ Smokers in Vietnam: An Exploratory Analysis
AbstractTozan, Y., Guevara, G., Kapur, R., Nugyen, T., Nugyen, N., Tozan, Y., Goldsamt, L., Cleland, C., Armstrong-Hough, M., Parekh, N., & Shelley, D. (n.d.).Publication year
2025Journal title
Cancer Epidemiology, Biomarkers & PreventionVolume
34Issue
12_SupplementPage(s)
80--80Abstract~Quantifying the lagged effects of climate variables on malaria risk in Eastern Uganda
AbstractKim, S., Nabukeera, B., Taremwa, Y., Ng’etich, M., Otieno, F., Cygu, S., Kajungu, D., Kiragga, A., & Tozan, Y. (n.d.).Publication year
2025Journal title
Am J Trop Med HygVolume
113Issue
6Page(s)
1256AbstractClimate change is anticipated to significantly affect malaria transmission. Previous research has shown lagged, nonlinear associations between climate variables and malaria risk, with highly context-specific exposure-lag-response relationship. Using weekly malaria case data collected between July 2018 and February 2023 from a health facility within the Iganga-Mayuge Health and Demographic Surveillance System site in Uganda and remotely sensed temperature and rainfall data, we quantified the associations between temperature and rainfall and risk of developing symptomatic malaria using a distributed lag nonlinear model. Furthermore, we investigated whether these associations varied by age group. Our analysis revealed a lag of 2 to 8 weeks between exposure to rainfall exceeding 200 mm/week and a significant increase in the risk of developing symptomatic malaria; no statistically significant lagged …Social and psychological mediators of sexual and physical male-perpetrated intimate partner violence against young African American women and problem alcohol use: the role of intimate and social drinking context
AbstractCapasso, A., Pahl, K., Tozan, Y., & DiClemente, R. (n.d.).Publication year
2025Journal title
Journal of Interpersonal ViolenceAbstractProblem alcohol use is prevalent among women who experience male-perpetrated intimate partner violence (IPV). However, the pathways by which this occurs remain poorly understood and understudied among African American women. This study sought to examine context-specific social and psychological mediators of this association. Using structural equation modeling (SEM), we tested a conceptual framework predicting problem alcohol use within 3 months of experiencing physical and/or sexual IPV. The sample included 508 young African American women (median age 21, interquartile range 19–22 years). A modified SEM met prespecified global and local fit index criteria. The model identified four indirect paths from IPV to problem alcohol use. Three of the paths were through the endorsement of drinking contexts: negative coping, social drinking, and intimate drinking. Negative coping and social drinking …Spatio-temporal modelling and prediction of malaria incidence in Mozambique using climatic indicators from 2001 to 2018
AbstractTozan, Y., Armando, C. J. J., Rocklöv, J., Sidat, M., Tozan, Y., Mavume, A. F. F., & Sewe, M. O. O. (n.d.).Publication year
2025Journal title
Scientific reportsVolume
15Issue
1Page(s)
11971AbstractAccurate malaria predictions are essential for implementing timely interventions, particularly in Mozambique, where climate factors strongly influence transmission. This study aims to develop and evaluate a spatial-temporal prediction model for malaria incidence in Mozambique for potential use in a malaria early warning system (MEWS). We used monthly data on malaria cases from 2001 to 2018 in Mozambique, the model incorporated lagged climate variables selected through Deviance Information Criterion (DIC), including mean temperature and precipitation (1-2 months), relative humidity (5-6 months), and Normalized Different Vegetation Index (NDVI) (3-4 months). Predictive distributions from monthly cross-validations were employed to calculate threshold exceedance probabilities, with district-specific thresholds set at the 75th percentile of historical monthly malaria incidence. The model's ability to predict high and low malaria seasons was evaluated using receiver operating characteristic (ROC) analysis. Results indicated that malaria incidence in Mozambique peaks from November to April, offering a predictive lead time of up to 4 months. The model demonstrated high predictive power with an area under the curve (AUC) of 0.897 (0.893-0.901), sensitivity of 0.835 (0.827-0.843), and specificity of 0.793 (0.787-0.798), underscoring its suitability for integration into a MEWS. Thus, incorporating climate information within a multisectoral approach is essential for enhancing malaria prevention interventions effectiveness.Spatio-temporal modelling and prediction of malaria incidence in Mozambique using climatic indicators from 2001 to 2018
AbstractArmando, C. J., Rocklöv, J., Sidat, M., Tozan, Y., Mavume, A. F., & Sewe, M. O. (n.d.).Publication year
2025Journal title
Scientific reportsVolume
15Issue
1AbstractAccurate malaria predictions are essential for implementing timely interventions, particularly in Mozambique, where climate factors strongly influence transmission. This study aims to develop and evaluate a spatial–temporal prediction model for malaria incidence in Mozambique for potential use in a malaria early warning system (MEWS). We used monthly data on malaria cases from 2001 to 2018 in Mozambique, the model incorporated lagged climate variables selected through Deviance Information Criterion (DIC), including mean temperature and precipitation (1–2 months), relative humidity (5–6 months), and Normalized Different Vegetation Index (NDVI) (3–4 months). Predictive distributions from monthly cross-validations were employed to calculate threshold exceedance probabilities, with district-specific thresholds set at the 75th percentile of historical monthly malaria incidence. The model’s ability to predict high and low malaria seasons was evaluated using receiver operating characteristic (ROC) analysis. Results indicated that malaria incidence in Mozambique peaks from November to April, offering a predictive lead time of up to 4 months. The model demonstrated high predictive power with an area under the curve (AUC) of 0.897 (0.893–0.901), sensitivity of 0.835 (0.827–0.843), and specificity of 0.793 (0.787–0.798), underscoring its suitability for integration into a MEWS. Thus, incorporating climate information within a multisectoral approach is essential for enhancing malaria prevention interventions effectiveness.The impact of armed conflict on vaccination coverage: a systematic review of empirical evidence from 1985 to 2025
AbstractTozan, Y., Headley, T. Y., Shay, C. W., & Tozan, Y. (n.d.).Publication year
2025Journal title
Conflict and HealthVolume
19Issue
1Page(s)
71Abstract~Trajectories of Physical Violence Against Latinas and Black Women: The Protective Role of Parents, Neighborhoods, and Schools
AbstractTozan, Y., Capasso, A., Tozan, Y., DiClemente, R. J., & Pahl, K. (n.d.).Publication year
2025Journal title
Violence against womenPage(s)
10778012251319752AbstractUnderstanding the heterogeneous experiences of violence experienced by Black and Latina women over the life course is critical to prevention. We identified four physical violence trajectories experienced by 361 Black and Latina women followed from ages 14 to 39: low/none (44.0%), persistent-moderate (36.8%), peak in the 20s (11.9%), and persistent-high (7.2%) violence exposure. Childhood abuse predicted membership in the three violence-exposed groups, whereas parental closeness, school academic orientation, and neighborhood safety were protective factors. Public health interventions aimed at preventing childhood trauma and ensuring safe interpersonal relationships and environments for girls to thrive are urgently needed.A pre-post evaluation study of a social media-based COVID-19 communication campaign to improve attitudes and behaviors toward COVID-19 vaccination in Tanzania
AbstractKim, S., Lilani, A., Redemptus, C., Campana, K., & Tozan, Y. (n.d.).Publication year
2024Journal title
PloS oneVolume
19Issue
5 MayAbstractIn Tanzania, the One by One: Target COVID-19 campaign was launched nationally in July 2022 to address the prevalent vaccine hesitancy and lack of confidence in COVID-19 vaccines. The campaign mobilized social media influencers and viral content with the ultimate goal of increasing COVID-19 vaccine uptake in the country. The objective of this study was to empirically assess the impact of the campaign on three outcomes: vaccine confidence, vaccine hesitancy, and vaccination status. Using programmatic data collected through an online survey before and after the campaign, we conducted a difference-in-difference (DiD) analysis and performed a crude, adjusted, and propensity score-matched analysis for each study outcome. Lastly, to observe whether there was any differential impact of the campaign across age groups, we repeated the analyses on age-stratified subgroups. Data included 5,804 survey responses, with 3,442 and 2,362 responses collected before and after the campaign, respectively. Although there was only weak evidence of increased COVID-19 vaccine confidence in the campaign-exposed group compared to the control group across all age groups, we observed a differential impact among different age groups. While no significant change was observed among young adults aged 18–24 years, the campaign exposure led to a statistically significant increase in vaccine confidence (weighted/adjusted DiD coefficient = 0.76; 95% CI: 0.06, 1.5; p-value = 0.034) and vaccination uptake (weighted/adjusted DiD coefficient = 1.69.; 95% CI: 1.02, 2.81; p-value = 0.023) among young adults aged 25–34 years. Among adults aged 35 years and above, the campaign exposure led to a significant decrease in vaccine hesitancy (weighted/adjusted DiD coefficient = -15; 95% CI: -21, -8.3; p-value