Yesim Tozan

Associate Professor of Global and Environmental Health

Professional overview

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.”

Education

BS, Environmental Engineering, Istanbul Technical University, Turkey

MS, Environmental Technology, Bogazici University, Turkey

MA, Public Affairs, Princeton University, Princeton, NJ

PhD, Public Affairs, Princeton University, Princeton, NJ

Areas of research and study

Cost Effectiveness

Cost-effective Health Programs and Policies

Economic Evaluation

Health Economics

Infectious Diseases

Prevention Interventions

Publications

Publications

Socioeconomic predictors of COVID-19- related health disparities among United States workers : A structural equation modeling study

Capasso, A., Kim, S., Ali, S. H., Jones, A. M., DiClemente, R. J., & Tozan, Y. (n.d.).

Publication year

2022

Journal title

PLOS global public health

Volume

2

Issue

2

10.1371/journal.pgph.0000117

Abstract

Abstract

The COVID-19 pandemic has disproportionately impacted the physical and mental health, and the economic stability, of specific population subgroups in different ways, deepening existing disparities. Essential workers have faced the greatest risk of exposure to COVID- 19; women have been burdened by caretaking responsibilities; and rural residents have experienced healthcare access barriers. Each of these factors did not occur on their own. While most research has so far focused on individual factors related to COVID-19 disparities, few have explored the complex relationships between the multiple components of COVID-19 vulnerabilities. Using structural equation modeling on a sample of United States (U.S.) workers (N = 2800), we aimed to 1) identify factor clusters that make up specific COVID-19 vulnerabilities, and 2) explore how these vulnerabilities affected specific subgroups, specifically essential workers, women and rural residents. We identified 3 COVID- 19 vulnerabilities: financial, mental health, and healthcare access; 9 out of 10 respondents experienced one; 15% reported all three. Essential workers [standardized coefficient (β) = 0.23; unstandardized coefficient (B) = 0.21, 95% CI = 0.17, 0.24] and rural residents (β = 0.13; B = 0.12, 95% CI = 0.09, 0.16) experienced more financial vulnerability than nonessential workers and non-rural residents, respectively. Women (β = 0.22; B = 0.65, 95% CI = 0.65, 0.74) experienced worse mental health than men; whereas essential workers reported better mental health (β = -0.08; B = -0.25, 95% CI = -0.38, -0.13) than other workers. Rural residents (β = 0.09; B = 0.15, 95% CI = 0.07, 0.24) experienced more healthcare access barriers than non-rural residents. Findings highlight how interrelated financial, mental health, and healthcare access vulnerabilities contribute to the disproportionate COVID- 19-related burden among U.S. workers. Policies to secure employment conditions, including fixed income and paid sick leave, are urgently needed to mitigate pandemic-associated disparities.

Socioeconomic predictors of COVID-19-related health disparities among United States workers: A structural equation modeling study

Tozan, Y., Capasso, A., Kim, S., Ali, S. H., Jones, A. M., DiClemente, R. J., & Tozan, Y. (n.d.).

Publication year

2022

Journal title

PLOS global public health

Volume

2

Issue

2

Page(s)

e0000117

Abstract

Abstract

The COVID-19 pandemic has disproportionately impacted the physical and mental health, and the economic stability, of specific population subgroups in different ways, deepening existing disparities. Essential workers have faced the greatest risk of exposure to COVID-19; women have been burdened by caretaking responsibilities; and rural residents have experienced healthcare access barriers. Each of these factors did not occur on their own. While most research has so far focused on individual factors related to COVID-19 disparities, few have explored the complex relationships between the multiple components of COVID-19 vulnerabilities. Using structural equation modeling on a sample of United States (U.S.) workers (N = 2800), we aimed to 1) identify factor clusters that make up specific COVID-19 vulnerabilities, and 2) explore how these vulnerabilities affected specific subgroups, specifically essential workers, women and rural residents. We identified 3 COVID-19 vulnerabilities: financial, mental health, and healthcare access; 9 out of 10 respondents experienced one; 15% reported all three. Essential workers [standardized coefficient (β) = 0.23; unstandardized coefficient (B) = 0.21, 95% CI = 0.17, 0.24] and rural residents (β = 0.13; B = 0.12, 95% CI = 0.09, 0.16) experienced more financial vulnerability than non-essential workers and non-rural residents, respectively. Women (β = 0.22; B = 0.65, 95% CI = 0.65, 0.74) experienced worse mental health than men; whereas essential workers reported better mental health (β = -0.08; B = -0.25, 95% CI = -0.38, -0.13) than other workers. Rural residents (β = 0.09; B = 0.15, 95% CI = 0.07, 0.24) experienced more healthcare access barriers than non-rural residents. Findings highlight how interrelated financial, mental health, and healthcare access vulnerabilities contribute to the disproportionate COVID-19-related burden among U.S. workers. Policies to secure employment conditions, including fixed income and paid sick leave, are urgently needed to mitigate pandemic-associated disparities.

Spatial variations in dengue transmission in schools in Thailand

Ratanawong, P., Kittayapong, P., Olanratmanee, P., Wilder-Smith, A., Byass, P., Tozan, Y., Dambach, P., Quiñonez, C. A., & Louis, V. R. (n.d.).

Publication year

2016

Journal title

PloS one

Volume

11

Issue

9

10.1371/journal.pone.0161895

Abstract

Abstract

Background: Dengue is an important neglected tropical disease, with more than half of the world's population living in dengue endemic areas. Good understanding of dengue transmission sites is a critical factor to implement effective vector control measures. Methods: A cohort of 1,811 students from 10 schools in rural, semi-rural and semi-urban Thailand participated in this study. Seroconversion data and location of participants' residences and schools were recorded to determine spatial patterns of dengue infections. Blood samples were taken to confirm dengue infections in participants at the beginning and the end of school term. Entomological factors included a survey of adult mosquito density using a portable vacuum aspirator during the school term and a follow up survey of breeding sites of Aedes vectors in schools after the school term. Clustering analyses were performed to detect spatial aggregation of dengue infections among participants. Results: A total of 57 dengue seroconversions were detected among the 1,655 participants who provided paired blood samples. Of the 57 confirmed dengue infections, 23 (40.0%) occurred in students from 6 (6.8%) of the 88 classrooms in 10 schools. Dengue infections did not show significant clustering by residential location in the study area. During the school term, a total of 66 Aedes aegypti mosquitoes were identified from the 278 mosquitoes caught in 50 classrooms of the 10 schools. In a follow-up survey of breeding sites, 484 out of 2,399 water containers surveyed (20.2%) were identified as active mosquito breeding sites. Discussion and Conclusion: Our findings suggest that dengue infections were clustered among schools and among classrooms within schools. The schools studied were found to contain a large number of different types of breeding sites. Aedes vector densities in schools were correlated with dengue infections and breeding sites in those schools. Given that only a small proportion of breeding sites in the schools were subjected to vector control measures (11%), this study emphasizes the urgent need to implement vector control strategies at schools, while maintaining efforts at the household level.

Spatial-temporal analysis of climate and socioeconomic conditions on cholera incidence in Mozambique from 2000 to 2018 : an ecological longitudinal retrospective study

Armando, C. J., Rocklöv, J., Sidat, M., Tozan, Y., Mavume, A. F., Bunker, A., & Sewe, M. O. (n.d.).

Publication year

2024

Journal title

BMJ open

Volume

14

Issue

8

10.1136/bmjopen-2023-082503

Abstract

Abstract

Objectives This study aims to assess both socioeconomic and climatic factors of cholera morbidity in Mozambique considering both spatial and temporal dimensions. Design An ecological longitudinal retrospective study using monthly provincial cholera cases from Mozambican Ministry of Health between 2000 and 2018. The cholera cases were linked to socioeconomic data from Mozambique Demographic and Health Surveys conducted in the period 2000-2018 and climatic data; relative humidity (RH), mean temperature, precipitation and Normalised Difference Vegetation Index (NDVI). A negative binomial regression model in a Bayesian framework was used to model cholera incidence while adjusting for the spatiotemporal covariance, lagged effect of environmental factors and the socioeconomic indicators. Setting Eleven provinces in Mozambique. Results Over the 19-year period, a total of 153 941 cholera cases were notified to the surveillance system in Mozambique. Risk of cholera increased with higher monthly mean temperatures above 24°C in comparison to the reference mean temperature of 23°C. At mean temperature of 19°C, cholera risk was higher at a lag of 5-6 months. At a shorter lag of 1 month, precipitation of 223.3 mm resulted in an 57% increase in cholera risk (relative risk, RR 1.57 (95% CI 1.06 to 2.31)). Cholera risk was greatest at 3 lag months with monthly NDVI of 0.137 (RR 1.220 (95% CI 1.042 to 1.430)), compared with the reference value of 0.2. At an RH of 54%, cholera RR was increased by 62% (RR 1.620 (95% CI 1.124 to 2.342)) at a lag of 4 months. We found that ownership of radio RR 0.29, (95% CI 0.109 to 0.776) and mobile phones RR 0.262 (95% CI 0.097 to 0.711) were significantly associated with low cholera risk. Conclusion The derived lagged patterns can provide appropriate lead times in a climate-driven cholera early warning system that could contribute to the prevention and management of outbreaks.

Spatial-temporal analysis of climate and socioeconomic conditions on cholera incidence in Mozambique from 2000 to 2018: an ecological longitudinal retrospective study

Tozan, Y., Armando, C. J. J., Rocklöv, J., Sidat, M., Tozan, Y., Mavume, A. F. F., Bunker, A., & Sewe, M. O. O. (n.d.).

Publication year

2024

Journal title

BMJ open

Volume

14

Issue

8

Page(s)

e082503

Abstract

Abstract

This study aims to assess both socioeconomic and climatic factors of cholera morbidity in Mozambique considering both spatial and temporal dimensions.

Spatio-temporal modelling and prediction of malaria incidence in Mozambique using climatic indicators from 2001 to 2018

Tozan, Y., Armando, C. J. J., Rocklöv, J., Sidat, M., Tozan, Y., Mavume, A. F. F., & Sewe, M. O. O. (n.d.).

Publication year

2025

Journal title

Scientific reports

Volume

15

Issue

1

Page(s)

11971

Abstract

Abstract

Accurate 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

Armando, C. J., Rocklöv, J., Sidat, M., Tozan, Y., Mavume, A. F., & Sewe, M. O. (n.d.).

Publication year

2025

Journal title

Scientific reports

Volume

15

Issue

1

10.1038/s41598-025-97072-6

Abstract

Abstract

Accurate 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 economic payoffs of integrated malaria control in the Zambian copperbelt between 1930 and 1950

Utzinger, J., Tozan, Y., Doumani, F., & Singer, B. H. (n.d.).

Publication year

2002

Journal title

Tropical Medicine and International Health

Volume

7

Issue

8

Page(s)

657-677

10.1046/j.1365-3156.2002.00916.x

Abstract

Abstract

It has long been suggested that malaria is delaying the economic development of countries that are most severely affected by the disease. Several studies have documented the economic consequences of malaria at the household level, primarily in communities engaged in subsistence farming. A missing element is the appraisal of the economic impact of malaria on the industrial and service sectors that will probably become the backbone of many developing economies. We estimate the economic effects of integrated malaria control implemented during the colonial period and sustained for 20 years in four copper mining communities of the former Northern Rhodesia (now Zambia). Integrated malaria control was characterized by strong emphasis on environmental management, while part of the mining communities also benefited from rapid diagnosis and treatment and the use of bednets. The programmes were highly successful as an estimated 14 122 deaths, 517 284 malaria attacks and 942 347 work shift losses were averted. Overall, 127 226 disability adjusted life years (DALYs) were averted per 3-year incremental period. The cumulative costs of malaria control interventions were US$ 11 169 472 (in 1995 US$). Because the control programmes were so effective, the mining companies attracted a large reservoir of migrant labourers and sustained healthy work forces. The programmes averted an estimated US$ 796 622 in direct treatment costs and US$ 5 678 745 in indirect costs as a result of reduced work absenteeism. Within a few years of programme initiation, Northern Rhodesia became the leading copper producer in Africa, and mining generated the dominant share of national income. Copper production and revenues, which increased dramatically during malaria control interventions, amounted to the equivalent of US$ 7.1 billion (in 1995 US$). Integrated malaria control in copper mining communities was a sound investment. It had payoff for public and occupational health, generally, and without it copper extraction and social and economic development would have been impossible.

The effectiveness of malaria camps as part of the Durgama Anchalare Malaria Nirakaran (DAMaN) program in Odisha, India : study protocol for a cluster-assigned quasi-experimental study

Ompad, D. C., Kessler, A., Van Eijk, A. M., Padhan, T. K., Haque, M. A., Sullivan, S. A., Tozan, Y., Rocklöv, J., Mohanty, S., Pradhan, M. M., Sahu, P. K., & Carlton, J. M. (n.d.).

Publication year

2021

Journal title

Global Health Action

Volume

14

Issue

1

10.1080/16549716.2021.1886458

Abstract

Abstract

The Indian state of Odisha has a longstanding battle with forest malaria. Many remote and rural villages have poor access to health care, a problem that is exacerbated during the rainy season when malaria transmission is at its peak. Approximately 62% of the rural population consists of tribal groups who are among the communities most negatively impacted by malaria. To address the persistently high rates of malaria in these remote regions, the Odisha State Malaria Control Program introduced ‘malaria camps’ in 2017 where teams of health workers visit villages to educate the population, enhance vector control methods, and perform village-wide screening and treatment. Malaria rates declined statewide, particularly in forested areas, following the introduction of the malaria camps, but the impact of the intervention is yet to be externally evaluated. This study protocol describes a cluster-assigned quasi-experimental stepped-wedge study with a pretest-posttest control group design that evaluates if malaria camps reduce the prevalence of malaria, compared to control villages which receive the usual malaria control interventions (e.g. IRS, ITNs), as detected by PCR.

The effectiveness of malaria camps as part of the malaria control program in Odisha, India

Tozan, Y., Ompad, D. C., Padhan, T. K., Kessler, A., Mohanty, S., Tozan, Y., Jones, A. M., van Eijk, A. M. M., Sullivan, S. A., Haque, M. A., Pradhan, M. M. M., Mohanty, S., Carlton, J. M., & Sahu, P. K. (n.d.).

Publication year

2023

Journal title

medRxiv : the preprint server for health sciences

Abstract

Abstract

Durgama Anchalare Malaria Nirakaran (DAMaN) is a multi-component malaria intervention for hard-to-reach villages in Odisha, India. The main component, Malaria Camps (MCs), consists of mass screening, treatment, education, and intensified vector control. We evaluated MC effectiveness using a quasi-experimental cluster-assigned stepped-wedge study with a pretest-posttest control group in 15 villages: six immediate (Arm A), six delayed (Arm B), and three previous interventions (Arm C). The primary outcome was PCR+ infection prevalence. Across all arms, the odds of PCR+ malaria were 54% lower at the third follow-up compared to baseline. A time (i.e., visit) x study arm interaction revealed significantly lower odds of PCR+ malaria in Arm A versus B at the third follow-up. The cost per person ranged between US$3-8, the cost per tested US$4-7, and the cost per treated US$82-1,614, per camp round. These results suggest that the DAMaN intervention is a promising, financially feasible approach for malaria control.

The effectiveness of malaria camps as part of the malaria control program in Odisha, India

Tozan, Y., Ompad, D. C., Padhan, T. K., Kessler, A., Tozan, Y., Jones, A. M., van Eijk, A. M. M., Sullivan, S. A., Haque, M. A., Pradhan, M. M. M., Mohanty, S., Carlton, J. M., & Sahu, P. K. (n.d.).

Publication year

2023

Journal title

Scientific reports

Volume

13

Issue

1

Page(s)

22998

Abstract

Abstract

Durgama Anchalare Malaria Nirakaran (DAMaN) is a multi-component malaria intervention for hard-to-reach villages in Odisha, India. The main component, malaria camps (MCs), consists of mass screening, treatment, education, and intensified vector control. We evaluated MC effectiveness using a quasi-experimental cluster-assigned stepped-wedge study with a pretest-posttest control group in 15 villages: six immediate (Arm A), six delayed (Arm B), and three previous interventions (Arm C). The primary outcome was PCR + Plasmodium infection prevalence. The time (i.e., baseline vs. follow-up 3) x study arm interaction term shows that there were statistically significant lower odds of PCR + Plasmodium infection in Arm A (AOR = 0.36, 95% CI = 0.17, 0.74) but not Arm C as compared to Arm B at the third follow-up. The cost per person ranged between US$3-8, the cost per tested US$4-9, and the cost per treated US$82-1,614, per camp round. These results suggest that the DAMaN intervention is a promising and financially feasible approach for malaria control.

The effectiveness of malaria camps as part of the malaria control program in Odisha, India

Ompad, D. C., Padhan, T. K., Kessler, A., Tozan, Y., Jones, A. M., van Eijk, A. M., Sullivan, S. A., Haque, M. A., Pradhan, M. M., Mohanty, S., Carlton, J. M., & Sahu, P. K. (n.d.).

Publication year

2023

Journal title

Scientific reports

Volume

13

Issue

1

10.1038/s41598-023-46220-x

Abstract

Abstract

Durgama Anchalare Malaria Nirakaran (DAMaN) is a multi-component malaria intervention for hard-to-reach villages in Odisha, India. The main component, malaria camps (MCs), consists of mass screening, treatment, education, and intensified vector control. We evaluated MC effectiveness using a quasi-experimental cluster-assigned stepped-wedge study with a pretest–posttest control group in 15 villages: six immediate (Arm A), six delayed (Arm B), and three previous interventions (Arm C). The primary outcome was PCR + Plasmodium infection prevalence. The time (i.e., baseline vs. follow-up 3) x study arm interaction term shows that there were statistically significant lower odds of PCR + Plasmodium infection in Arm A (AOR = 0.36, 95% CI = 0.17, 0.74) but not Arm C as compared to Arm B at the third follow-up. The cost per person ranged between US$3–8, the cost per tested US$4–9, and the cost per treated US$82–1,614, per camp round. These results suggest that the DAMaN intervention is a promising and financially feasible approach for malaria control.

The efficacy and cost-effectiveness of a family-based economic empowerment intervention (Suubi + Adherence) on suppression of HIV viral loads among adolescents living with HIV : results from a Cluster Randomized Controlled Trial in southern Uganda

Tozan, Y., Capasso, A., Sun, S., Neilands, T. B., Damulira, C., Namuwonge, F., Nakigozi, G., Mwebembezi, A., Mukasa, B., Sensoy Bahar, O., Nabunya, P., Mellins, C. A., McKay, M. M., & Ssewamala, F. M. (n.d.).

Publication year

2021

Journal title

Journal of the International AIDS Society

Volume

24

Issue

6

10.1002/jia2.25752

Abstract

Abstract

Introduction: Evidence from low-resource settings indicates that economic insecurity is a major barrier to HIV treatment adherence. Economic empowerment (EE) interventions have the potential to improve adherence outcomes among adolescents living with HIV (ALWHIV) by mitigating the effects of poverty. This study aims to assess the efficacy and cost-effectiveness of a savings-led family-based EE intervention, Suubi + Adherence, aimed at improving antiretroviral therapy (ART) adherence outcomes ALWHIV in Uganda. Methods: Adolescents (mean age 12 years at enrolment; 56% female) receiving ART for HIV at 39 health centres were randomized to Suubi + Adherence intervention (n = 358) or bolstered standard of care (BSOC; n = 344). A difference-in-differences analysis was employed to assess the change in the proportion of virally suppressed adolescents (HIV RNA viral load

The impact of insecticide-treated school uniforms on dengue infections in school-aged children : Study protocol for a randomised controlled trial in Thailand

Wilder-Smith, A., Byass, P., Olanratmanee, P., Maskhao, P., Sringernyuang, L., Logan, J. G., Lindsay, S. W., Banks, S., Gubler, D., Louis, V. R., Tozan, Y., & Kittayapong, P. (n.d.).

Publication year

2012

Journal title

Trials

Volume

13

10.1186/1745-6215-13-212

Abstract

Abstract

Background: There is an urgent need to protect children against dengue since this age group is particularly sensitive to the disease. Since dengue vectors are active mainly during the day, a potential target for control should be schools where children spend a considerable amount of their day. School uniforms are the cultural norm in most developing countries, worn throughout the day. We hypothesise that insecticide-treated school uniforms will reduce the incidence of dengue infection in school-aged children. Our objective is to determine the impact of impregnated school uniforms on dengue incidence.Methods: A randomised controlled trial will be conducted in eastern Thailand in a group of schools with approximately 2,000 students aged 7-18 years. Pre-fabricated school uniforms will be commercially treated to ensure consistent, high-quality insecticide impregnation with permethrin. A double-blind, randomised, crossover trial at the school level will cover two dengue transmission seasons.Discussion: Practical issues and plans concerning intervention implementation, evaluation, analysing and interpreting the data, and possible policy implications arising from the trial are discussed.Trial registration: clinicaltrial.gov. Registration number: NCT01563640.

The Mosquito, the Virus, the Climate : An Unforeseen Réunion in 2018

DiSera, L., Sjödin, H., Rocklöv, J., Tozan, Y., Súdre, B., Zeller, H., & Muñoz, Á. G. (n.d.).

Publication year

2020

Journal title

GeoHealth

Volume

4

Issue

8

10.1029/2020GH000253

Abstract

Abstract

The 2018 outbreak of dengue in the French overseas department of Réunion was unprecedented in size and spread across the island. This research focuses on the cause of the outbreak, asserting that climate played a large role in the proliferation of the Aedes albopictus mosquitoes, which transmitted the disease, and led to the dengue outbreak in early 2018. A stage-structured model was run using observed temperature and rainfall data to simulate the life cycle and abundance of the Ae. albopictus mosquito. Further, the model was forced with bias-corrected subseasonal forecasts to determine if the event could have been forecast up to 4 weeks in advance. With unseasonably warm temperatures remaining above 25°C, along with large tropical-cyclone-related rainfall events accumulating 10–15 mm per event, the modeled Ae. albopictus mosquito abundance did not decrease during the second half of 2017, contrary to the normal behavior, likely contributing to the large dengue outbreak in early 2018. Although subseasonal forecasts of rainfall for the December–January period in Réunion are skillful up to 4 weeks in advance, the outbreak could only have been forecast 2 weeks in advance, which along with seasonal forecast information could have provided enough time to enhance preparedness measures. Our research demonstrates the potential of using state-of-the-art subseasonal climate forecasts to produce actionable subseasonal dengue predictions. To the best of the authors' knowledge, this is the first time subseasonal forecasts have been used this way.

The synergistic impact of Universal Health Coverage and Global Health Security on health service delivery during the Coronavirus Disease-19 pandemic : A difference-indifference study of childhood immunization coverage from 192 countries

Kim, S., Headley, T. Y., & Tozan, Y. (n.d.).

Publication year

2024

Journal title

PLOS global public health

Volume

4

Issue

5 May

10.1371/journal.pgph.0003205

Abstract

Abstract

Universal Health Coverage (UHC) and Global Health Security (GHS) are two high-priority global health agendas that seek to foster health system resilience against health emergencies. Many countries have had to prioritize one agenda over the other due to scarce resources and political pressures. To aid policymakers’ decision-making, this study investigated the individual and synergistic effects of countries’ UHC and GHS capacities in safeguarding essential health service delivery during the COVID-19 pandemic. We used a quasi-experimental difference-in-difference methodology to quantify the relationship between 192 countries’ progress towards UHC and GHS and those countries’ abilities to provide 12 essential childhood immunization services between 2015 and 2021. We used the 2019 UHC Service Coverage Index (SCI) to divide countries into a “high UHC group” (UHC SCI≥75) and the rest (UHC SCI 75), and similarly used the 2019 GHS Index (GHSI) to divide countries into a “high GHS group” (GHSI≥65) and the rest (GHSI

The synergistic impact of Universal Health Coverage and Global Health Security on health service delivery during the Coronavirus Disease-19 pandemic: A difference-in-difference study of childhood immunization coverage from 192 countries

Tozan, Y., Kim, S., Headley, T. Y., & Tozan, Y. (n.d.).

Publication year

2024

Journal title

PLOS global public health

Volume

4

Issue

5

Page(s)

e0003205

Abstract

Abstract

Universal Health Coverage (UHC) and Global Health Security (GHS) are two high-priority global health agendas that seek to foster health system resilience against health emergencies. Many countries have had to prioritize one agenda over the other due to scarce resources and political pressures. To aid policymakers' decision-making, this study investigated the individual and synergistic effects of countries' UHC and GHS capacities in safeguarding essential health service delivery during the COVID-19 pandemic. We used a quasi-experimental difference-in-difference methodology to quantify the relationship between 192 countries' progress towards UHC and GHS and those countries' abilities to provide 12 essential childhood immunization services between 2015 and 2021. We used the 2019 UHC Service Coverage Index (SCI) to divide countries into a "high UHC group" (UHC SCI≥75) and the rest (UHC SCI 75), and similarly used the 2019 GHS Index (GHSI) to divide countries into a "high GHS group" (GHSI≥65) and the rest (GHSI

Trajectories of Physical Violence Against Latinas and Black Women : The Protective Role of Parents, Neighborhoods, and Schools

Capasso, A., Tozan, Y., DiClemente, R. J., & Pahl, K. (n.d.).

Publication year

2025

Journal title

Violence Against Women

10.1177/10778012251319752

Abstract

Abstract

Understanding 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.

Trajectories of Physical Violence Against Latinas and Black Women: The Protective Role of Parents, Neighborhoods, and Schools

Tozan, Y., Capasso, A., Tozan, Y., DiClemente, R. J., & Pahl, K. (n.d.).

Publication year

2025

Journal title

Violence against women

Page(s)

10778012251319752

Abstract

Abstract

Understanding 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.

Transmission dynamics of dengue and chikungunya in a changing climate : do we understand the eco-evolutionary response?

Tozan, Y., Sjödin, H., Muñoz, Á. G., & Rocklöv, J. (n.d.).

Publication year

2020

Journal title

Expert Review of Anti-Infective Therapy

Volume

18

Issue

12

Page(s)

1187-1193

10.1080/14787210.2020.1794814

Abstract

Abstract

Introduction: We are witnessing an alarming increase in the burden and range of mosquito-borne arboviral diseases. The transmission dynamics of arboviral diseases is highly sensitive to climate and weather and is further affected by non-climatic factors such as human mobility, urbanization, and disease control. As evidence also suggests, climate-driven changes in species interactions may trigger evolutionary responses in both vectors and pathogens with important consequences for disease transmission patterns. Areas covered: Focusing on dengue and chikungunya, we review the current knowledge and challenges in our understanding of disease risk in a rapidly changing climate. We identify the most critical research gaps that limit the predictive skill of arbovirus risk models and the development of early warning systems, and conclude by highlighting the potentially important research directions to stimulate progress in this field. Expert opinion: Future studies that aim to predict the risk of arboviral diseases need to consider the interactions between climate modes at different timescales, the effects of the many non-climatic drivers, as well as the potential for climate-driven adaptation and evolution in vectors and pathogens. An important outcome of such studies would be an enhanced ability to promulgate early warning information, initiate adequate response, and enhance preparedness capacity.

Trends and predictors of COVID-19 information sources and their relationship with knowledge and beliefs related to the pandemic : Nationwide cross-sectional study

Ali, S. H., Foreman, J., Tozan, Y., Capasso, A., Jones, A. M., & DiClemente, R. J. (n.d.).

Publication year

2020

Journal title

JMIR Public Health and Surveillance

Volume

6

Issue

4

10.2196/21071

Abstract

Abstract

Background: During the COVID-19 pandemic, there is a heightened need to understand health information seeking behaviors to address disparities in knowledge and beliefs about the crisis. Objective: This study assessed sociodemographic predictors of the use and trust of different COVID-19 information sources, as well as the association between information sources and knowledge and beliefs about the pandemic. Methods: An online survey was conducted among US adults in two rounds during March and April 2020 using advertisement-based recruitment on social media. Participants were asked about their use of 11 different COVID-19 information sources as well as their most trusted source of information. The selection of COVID-related knowledge and belief questions was based on past empirical literature and salient concerns at the time of survey implementation. Results: The sample consisted of 11,242 participants. When combined, traditional media sources (television, radio, podcasts, or newspapers) were the largest sources of COVID-19 information (91.2%). Among those using mainstream media sources for COVID-19 information (n=7811, 69.5%), popular outlets included CNN (24.0%), Fox News (19.3%), and other local or national networks (35.2%). The largest individual information source was government websites (87.6%). They were also the most trusted source of information (43.3%), although the odds of trusting government websites were lower among males (adjusted odds ratio [AOR] 0.58, 95% CI 0.53-0.63) and those aged 40-59 years and ≥60 years compared to those aged 18-39 years (AOR 0.83, 95% CI 0.74-0.92; AOR 0.62, 95% CI 0.54-0.71). Participants used an average of 6.1 sources (SD 2.3). Participants who were male, aged 40-59 years or ≥60 years; not working, unemployed, or retired; or Republican were likely to use fewer sources while those with children and higher educational attainment were likely to use more sources. Participants surveyed in April were markedly less likely to use (AOR 0.41, 95% CI 0.35-0.46) and trust (AOR 0.51, 95% CI 0.47-0.56) government sources. The association between information source and COVID-19 knowledge was mixed, while many COVID-19 beliefs were significantly predicted by information source; similar trends were observed with reliance on different types of mainstream media outlets. Conclusions: COVID-19 information source was significantly determined by participant sociodemographic characteristics and was also associated with both knowledge and beliefs about the pandemic. Study findings can help inform COVID-19 health communication campaigns and highlight the impact of using a variety of different and trusted information sources.

Understanding COVID-19 vaccine hesitancy in Meghalaya, India : Multiple correspondence and agglomerative hierarchical cluster analyses

Kim, S., Sarkar, R., Kumar, S., Lewis, M. G., Tozan, Y., & Albert, S. (n.d.).

Publication year

2024

Journal title

PLOS global public health

Volume

4

Issue

2

10.1371/journal.pgph.0002250

Abstract

Abstract

Meghalaya, a state in the northeastern region of India, had a markedly low vaccine uptake compared to the other states in the country when COVID-19 vaccines were being rolled out in 2021. This study aimed to characterize the distinct vaccine-hesitant subpopulations in healthcare and community settings in Meghalaya state in the early days of the vaccination program. We used data from a cross-sectional survey that was administered to 200 healthcare workers (HCWs) and 200 community members, who were a priori identified as 'vaccine- eligible' and 'vaccine-hesitant,' in Shillong city, Meghalaya, in May 2021. The questionnaire collected information on participants' sociodemographic characteristics, COVID-19 history, and presence of medical comorbidities. Participants were also asked to provide a dichotomous answer to a set of 19 questions, probing the reasons for their hesitancy towards COVID-19 vaccines. A multiple correspondence analysis, followed by an agglomerative hierarchical cluster analysis, was performed to identify the distinct clusters of vaccine-hesitant participants. We identified seven clusters: indecisive HCWs (n = 71), HCWs skeptical of COVID-19 and COVID-19 vaccines (n = 128), highly educated male tribal/clan leaders concerned about infertility and future pregnancies (n = 14), less educated adults influenced by leaders and family (n = 47), older adults worried about vaccine safety (n = 76), middle-aged adults without young children (n = 56), and highly educated ethnic/religious minorities with misinformation (n = 8). Across all the clusters, perceived logistical challenges associated with receiving the vaccine was identified as a common factor contributing to vaccine hesitancy. Our study findings provide valuable insights for local and state health authorities to effectively target distinct subgroups of vaccine-hesitant populations with tailored health messaging, and also call for a comprehensive approach to address the common drivers of vaccine hesitancy in communities with low vaccination rates.

Understanding COVID-19 vaccine hesitancy in Meghalaya, India: Multiple correspondence and agglomerative hierarchical cluster analyses

Tozan, Y., Kim, S., Sarkar, R., Kumar, S., Lewis, M. G., Tozan, Y., & Albert, S. (n.d.).

Publication year

2024

Journal title

PLOS global public health

Volume

4

Issue

2

Page(s)

e0002250

Abstract

Abstract

Meghalaya, a state in the northeastern region of India, had a markedly low vaccine uptake compared to the other states in the country when COVID-19 vaccines were being rolled out in 2021. This study aimed to characterize the distinct vaccine-hesitant subpopulations in healthcare and community settings in Meghalaya state in the early days of the vaccination program. We used data from a cross-sectional survey that was administered to 200 healthcare workers (HCWs) and 200 community members, who were a priori identified as 'vaccine-eligible' and 'vaccine-hesitant,' in Shillong city, Meghalaya, in May 2021. The questionnaire collected information on participants' sociodemographic characteristics, COVID-19 history, and presence of medical comorbidities. Participants were also asked to provide a dichotomous answer to a set of 19 questions, probing the reasons for their hesitancy towards COVID-19 vaccines. A multiple correspondence analysis, followed by an agglomerative hierarchical cluster analysis, was performed to identify the distinct clusters of vaccine-hesitant participants. We identified seven clusters: indecisive HCWs (n = 71), HCWs skeptical of COVID-19 and COVID-19 vaccines (n = 128), highly educated male tribal/clan leaders concerned about infertility and future pregnancies (n = 14), less educated adults influenced by leaders and family (n = 47), older adults worried about vaccine safety (n = 76), middle-aged adults without young children (n = 56), and highly educated ethnic/religious minorities with misinformation (n = 8). Across all the clusters, perceived logistical challenges associated with receiving the vaccine was identified as a common factor contributing to vaccine hesitancy. Our study findings provide valuable insights for local and state health authorities to effectively target distinct subgroups of vaccine-hesitant populations with tailored health messaging, and also call for a comprehensive approach to address the common drivers of vaccine hesitancy in communities with low vaccination rates.

Universal healthcare coverage and health service delivery before and during the COVID- 19 pandemic : A difference-in-difference study of childhood immunization coverage from 195 countries

Kim, S., Headley, T. Y., & Tozan, Y. (n.d.).

Publication year

2022

Journal title

PLoS Medicine

Volume

19

Issue

8

10.1371/journal.pmed.1004060

Abstract

Abstract

Background Several studies have indicated that universal health coverage (UHC) improves health service utilization and outcomes in countries. These studies, however, have primarily assessed UHC's peacetime impact, limiting our understanding of UHC's potential protective effects during public health crises such as the Coronavirus Disease 2019 (COVID-19) pandemic. We empirically explored whether countries' progress toward UHC is associated with differential COVID-19 impacts on childhood immunization coverage. Methods and findings Using a quasi-experimental difference-in-difference (DiD) methodology, we quantified the relationship between UHC and childhood immunization coverage before and during the COVID-19 pandemic. The analysis considered 195 World Health Organization (WHO) member states and their ability to provision 12 out of 14 childhood vaccines between 2010 and 2020 as an outcome. We used the 2019 UHC Service Coverage Index (UHC SCI) to divide countries into a "high UHC index"group (UHC SCI ≥80) and the rest. All analyses included potential confounders including the calendar year, countries' income group per the World Bank classification, countries' geographical region as defined by WHO, and countries' preparedness for an epidemic/pandemic as represented by the Global Health Security Index 2019. For robustness, we replicated the analysis using a lower cutoff value of 50 for the UHC index. A total of 20,230 country-year observations were included in the study. The DiD estimators indicated that countries with a high UHC index (UHC SCI ≥80, n = 35) had a 2.70% smaller reduction in childhood immunization coverage during the pandemic year of 2020 as compared to the countries with UHC index less than 80 (DiD coefficient 2.70; 95% CI: 0.75, 4.65; p-value = 0.007). This relationship, however, became statistically nonsignificant at the lower cutoff value of UHC SCI

Use of insecticide-treated school uniforms for prevention of dengue in schoolchildren : A cost-effectiveness analysis

Tozan, Y., Ratanawong, P., Louis, V. R., Kittayapong, P., & Wilder-Smith, A. (n.d.).

Publication year

2014

Journal title

PloS one

Volume

9

Issue

9

10.1371/journal.pone.0108017

Abstract

Abstract

Background: Dengue-related illness is a leading cause of hospitalization and death, particularly among children. Practical, acceptable and affordable measures are urgently needed to protect this age group. Schools where children spend most of their day is proposed as an ideal setting to implement preventive strategies against day-biting Aedes mosquitoes. The use of insecticide-treated school uniforms is a promising strategy currently under investigation.Methods: Using a decision-analytic model, we evaluated the cost-effectiveness of the use of insecticide-treated school uniforms for prevention of dengue, compared with a ''do-nothing'' alternative, in schoolchildren from the societal perspective. We explored how the potential economic value of the intervention varied under various scenarios of intervention effectiveness and cost, as well as dengue infection risk in school-aged children, using data specific to Thailand.Results: At an average dengue incidence rate of 5.8% per year in school-aged children, the intervention was cost-effective (ICER≤$16,440) in a variety of scenarios when the intervention cost per child was $5.3 or less and the intervention effectiveness was 50% or higher. In fact, the intervention was cost saving (ICER,0) in all scenarios in which the intervention cost per child was $2.9 or less per year and the intervention effectiveness was 50% or higher. The results suggested that this intervention would be of no interest to Thai policy makers when the intervention cost per child was $10.6 or higher per year regardless of intervention effectiveness (ICER>$16,440).Conclusions: Our results present the potential economic value of the use of insecticide-treated uniforms for prevention of dengue in schoolchildren in a typical dengue endemic setting and highlight the urgent need for additional research on this intervention.