David W Dowdy

Johns Hopkins University | JHU · Department of Epidemiology

Background Rapid diagnosis of tuberculosis (TB) is important for improving outcomes and reducing transmission. Previous studies assessing the impact of Xpert MTB/RIF (Xpert), a molecular assay that provides results within 2 h, on mortality have been inconclusive. In this planned analysis of a pragmatic cluster-randomized trial in Uganda, we assesse...

Introduction Tuberculosis (TB) preventive treatment (TPT) is recommended for people living with HIV (PLHIV) in high TB burden settings. While 6 months of daily isoniazid remains widely used, shorter regimens are now available. However, little is known about preferences of PLHIV for key features of TPT regimens. Methods From July to November 2022,...

Background Short-course tuberculosis prevention regimens, including 12 weeks of isoniazid and rifapentine (3HP), are increasingly used in high TB-burden countries. Despite established safety and tolerability in efficacy trials, 3HP-related adverse events (AE) could differ in routine settings. Real-world data on AE type, frequency, and timing is cru...

Three months of isoniazid-rifapentine (3HP) is being scaled up for tuberculosis (TB) preventive treatment (TPT) among people living with HIV (PLHIV) in high-burden settings. More evidence is needed to identify factors influencing successful 3HP delivery. We conducted a qualitative assessment of 3HP delivery nested within the 3HP Options Trial, whic...

Understanding the epidemiology and ecology of yellow fever in endemic regions is critical for preventing future outbreaks. Ghana is a high-risk country for yellow fever. In this study we estimate the disease burden, ecological cycles, and areas at risk for yellow fever in Ghana based on historical outbreaks. We identify 2387 cases and 888 deaths (c...

Three months of isoniazid-rifapentine (3HP) is being scaled up for tuberculosis (TB) preventive treatment (TPT) among people living with HIV (PLHIV) in high-burden settings. More evidence is needed to identify factors influencing successful 3HP delivery. We conducted a qualitative assessment of 3HP delivery nested within the 3HP Options Trial, whic...

Background Household contact investigation (HCI) is an effective and widely used approach to identify persons with tuberculosis (TB) disease and infection, globally. Despite widespread recommendations for use of HCI, there is limited understanding of the influence and value of contact investigation for participants, and how household contact invest...

Introduction Antiretroviral therapy (ART) and tuberculosis preventive treatment (TPT) both prevent tuberculosis (TB) disease and deaths among people living with HIV. Differentiated care models, including community‐based care, can increase the uptake of ART and TPT to prevent TB in settings with a high burden of HIV‐associated TB, particularly among...

As global adoption of antiretroviral therapy extends the lifespan of People Living with HIV (PLHIV) through viral suppression, the risk of comorbid conditions such as hypertension has risen, creating a need for effective, scalable interventions to manage comorbidities in PLHIV. The Heart, Lung, and Blood Co-morbiditieS Implementation Models in Peop...

Background With numerous trials investigating novel drug combinations to treat tuberculosis, we aimed to evaluate the extent to which future improvements in tuberculosis treatment regimens could offset potential increases in drug costs. Methods In this modelling analysis, we used an ingredients-based approach to estimate prices at which novel regi...

Objectives Expansion of ART and increases to life expectancy have led to aging among people living with HIV (PWH). Design Kenyan decisionmakers need accurate forecasts of the age distribution of PWH to inform future policies. Methods We developed a model of HIV in Kenya, calibrated to historical estimates of HIV epidemiology. We forecasted change...

Background Laboratory networks provide services through onsite testing or through specimen transport to higher-tier laboratories. This decision is based on the interplay of testing characteristics, treatment characteristics, and epidemiological characteristics. Objectives Our objective was to develop a generalizable model using the threshold appro...

Background Expanding access to shorter regimens for tuberculosis (TB) prevention, such as once-weekly isoniazid and rifapentine taken for 3 months (3HP), is critical for reducing global TB burden among people living with HIV (PLHIV). Our coprimary hypotheses were that high levels of acceptance and completion of 3HP could be achieved with delivery s...

Background In settings with large case detection gaps, active case-finding (ACF) may play a critical role in the uberculosis (TB) response. However, ACF is resource intensive, and its effectiveness depends on whether people detected with TB through ACF might otherwise spontaneously resolve or be diagnosed through routine care. We analysed the poten...

BACKGROUND Both 1 month of daily (1HP) and 3 months of weekly (3HP) isoniazid-rifapentine are recommended as short-course regimens for TB prevention among people living with HIV (PLHIV). We aimed to assess acceptability and preferences for 1HP vs. 3HP among PLHIV. METHODS In a cross-sectional survey among PLHIV at an HIV clinic in Kampala, Uganda,...

Rationale C-reactive protein (CRP) has demonstrated utility as a point-of-care triage test for tuberculosis (TB) in clinical settings, particularly among people with HIV, but its performance for general-population TB screening is not well characterized. Objective To assess the accuracy of CRP for detecting pulmonary TB disease among individuals und...

Background In 2020, the WHO-approved Molbio Truenat platform and MTB assays to detect Mycobacterium tuberculosis complex (MTB) and resistance to rifampicin directly on sputum specimens. This primary health care center-based trial in Mozambique and Tanzania investigates the effect of Truenat platform/MTB assays (intervention arm) combined with rapid...

Background Diagnostic testing for TB needs to optimize access, turnaround time and thus time to treatment initiation and cost. Point of care (POC) testing optimizes the former, but additional costs beyond the test cost alone might be drivers of overall cost in a POC testing strategy, especially in low-and-middle-income settings. Methods We estimat...

Social events and stressful settings can be catalysts for alcohol consumption. Motivational enhancement therapy (MET) and cognitive behavioral therapy (CBT) are widely used in alcohol interventions. We assessed how alcohol consumption varied across three types of days (positive/social, negative/stressful, and neutral) among hazardous alcohol users...

Background Although West Africa has the largest burden of Yellow Fever (YF) cases globally, less is known about YF dynamics in this region. YF virus is thought to circulate via three transmission cycles in Africa: the sylvatic, savannah/intermediate, and urban cycles. Understanding the relative contribution of each cycle and the populations at risk...

Background Computer-aided detection (CAD) using artificial intelligence (AI) to analyze chest radiographs is an important tool for community tuberculosis (TB) screening in high burden countries. Most current algorithms use a universal cut-off score to select individuals for confirmatory TB testing; however, using a tailored cut-off based on client...

To better evaluate the cost-effectiveness of active case finding for tuberculosis, a framework for estimating long-term cost and impact is needed. We outline such a framework and highlight the need for consensus estimates of which costs to measure; averted morbidity, mortality, and transmission; measurable short-term outcomes; and meaningful cost-e...

Introduction Geographical mobility, the movement of individuals or populations, may increase an individual’s risk of acquiring or transmitting infectious diseases, including HIV, tuberculosis, malaria and COVID-19. Many studies have collected information on short-term mobility through self-reported travel histories or using GPS trackers, but there...

Background “Trace” results on Xpert MTB/RIF Ultra (“Ultra”) – a molecular diagnostic test for tuberculosis (TB) – are often interpreted as an indication for TB treatment, but may also represent detection of nonviable bacilli or analytical error. In community screening settings where individual TB risk is low, there is limited guidance on how to int...

Background Several clinical trials of tuberculosis preventive treatment (TPT) for household contacts of patients with multidrug- or rifampin-resistant tuberculosis (MDR/RR-TB) are nearing completion. The potential benefits of delivering TPT to MDR/RR-TB contacts extend beyond the outcomes that clinical trials can measure. Methods We developed an a...

Background Tuberculosis (TB) preventive treatment (TPT) is recommended for people living with HIV (PLHIV) in high TB burden settings. While 6 months of daily isoniazid remains widely used, shorter regimens are now available. However, little is known about preferences of PLHIV for key features of TPT regimens. Methods We conducted a discrete choice...

Background In 2020, the WHO-approved Molbio Truenat platform and MTB assays to detect Mycobacterium tuberculosis complex (MTB) and resistance to rifampicin directly on sputum specimens. This primary health care center-based trial in Mozambique and Tanzania investigates the effect of Truenat platform/MTB assays (intervention arm) combined with rapid...

BACKGROUND: TB-related stigma hampers access to diagnosis and treatment, making it important to understand the demographic and clinical characteristics associated with perceived TB stigma. TB stigma has not been studied in household contacts before, yet they comprise an important population for epidemic control, with high risk of infection.METHOD:...

Introduction: In high-burden settings, low-complexity screening tests for tuberculosis (TB) could expand the reach of community-based case-finding efforts. The potential costs and cost-effectiveness of approaches incorporating these tests are poorly understood. Methods: We developed a microsimulation model assessing three approaches to community...

Background Tuberculosis(TB) is among the leading causes of infectious death worldwide. Contact investigation is an evidence-based, World Health Organisation-endorsed intervention for timely TB diagnosis, treatment, and prevention but has not been widely and effectively implemented. Methods We are conducting a stepped-wedge, cluster-randomised, hyb...

People with tuberculosis (TB) are often lost to follow-up during treatment transition to another facility. These losses may result in substantial morbidity and mortality but are rarely recorded. We conducted a record review on adults diagnosed with TB at 11 hospitals in Limpopo, South Africa, who were subsequently transferred to a local clinic to i...

Background: Guidelines and implementation of tuberculosis preventive treatment (TPT) vary by age and HIV status. Specifically, TPT is strongly recommended for people living with HIV/AIDS (PLWHA) and household contacts younger than 5 years but only conditionally recommended for older contacts. Cost remains a major barrier to implementation. The aim...

Background Each year, 1 million children develop TB resulting in over 200,000 child deaths. TB preventive treatment (TPT) is highly effective in preventing TB but remains poorly implemented for household child contacts. Home-based child contact management and TPT services may improve access to care. In this study, we aim to evaluate the effectivene...

99DOTS is a low-cost digital adherence technology that allows people with tuberculosis (TB) to self-report treatment adherence. There are limited data on its implementation, feasibility, and acceptability from sub-Saharan Africa. We conducted a longitudinal analysis and cross-sectional surveys nested within a stepped-wedge randomized trial at 18 he...

Background Tuberculosis (TB) is among the leading causes of infectious death worldwide. Contact investigation is an evidence-based, World Health Organisation-endorsed intervention for timely TB diagnosis, treatment, and prevention but has not been widely and effectively implemented. Methods We are conducting a stepped-wedge, cluster-randomised, hyb...

Background Implementation science offers a systematic approach to adapting innovations and delivery strategies to new contexts but has yet to be widely applied in low- and middle-income countries. The Fogarty Center for Global Health Studies is sponsoring a special series, “Global Implementation Science Case Studies,” to address this gap. Methods...

Background: Our study aims to examine the factor structure, validity, and reliability of the combined scale Patient Health Questionnaire Anxiety and Depression Scale (PHQ-ADS) among people with HIV (PWH) in Vietnam. Methods: Baseline data from an alcohol-reduction intervention trial among ART clients in Thai Nguyen, Vietnam were used for this an...

BACKGROUND: Twelve weeks of weekly isoniazid and rifapentine (3HP) prevents TB disease among people with HIV (PWH), but the costs to people of taking TB preventive treatment is not well described.METHODS: We surveyed PWH who initiated 3HP at a large urban HIV/AIDS clinic in Kampala, Uganda, as part of a larger trial. We estimated the cost of one 3H...

Background: Point-of-care (POC) nucleic acid testing for diagnosis of HIV in infants facilitates earlier initiation of antiretroviral therapy (ART) than with centralised (standard-of-care, SOC) testing, but can be more expensive. We evaluated cost-effectiveness data from mathematical models comparing POC with SOC to provide global policy guidance....

Background Phosphatidylethanol (PEth) is a biomarker for recent alcohol consumption that would ideally validate self‐reported alcohol consumption behaviors. We assessed the relationship between PEth and several self‐reported alcohol consumption metrics among hazardous alcohol users living with HIV in Vietnam. Methods Participants in a three‐arm ra...

Introduction In South Africa, Community Caregivers (CCGs) visit households to provide basic healthcare services including those for tuberculosis and HIV. However, CCG workloads, costs, and time burden are largely unknown. Our objective was to assess the workloads and operational costs for CCG teams operating in different settings in South Africa....

Background Systematic screening is a potential tool for reducing the prevalence of tuberculosis and counteracting COVID-related disruptions in care. Repeated community-wide screening can also measure changes in the prevalence of tuberculosis over time. Methods We conducted serial, cross-sectional tuberculosis case-finding campaigns in one communit...

Vaccine discovery, financing, and distribution offer technical challenges requiring difficult choices. Patients, parents, providers, and politicians all must decide about who, when, where to vaccinate. Billions if not trillions of dollars and millions of lives depend on getting these choices right. Economics, the science of choice under uncertainty...

Vaccine discovery, financing, and distribution offer technical challenges requiring difficult choices. Patients, parents, providers, and politicians all must decide about who, when, where to vaccinate. Billions if not trillions of dollars and millions of lives depend on getting these choices right. Economics, the science of choice under uncertainty...

Background: Several clinical trials of tuberculosis preventive treatment (TPT) for household contacts of patients with multidrug resistant tuberculosis (MDR TB) are nearing completion. The potential benefits of TPT for MDR TB contacts extend beyond the outcomes that clinical trials can measure. Methods: We developed an agent based, household struct...

Objective: We aimed to evaluate safety of 3 months weekly isoniazid-rifapentine (3HP) for tuberculosis (TB) prevention when co-administered with dolutegravir-based antiretroviral therapy (TLD), and compare viral suppression among those initiating TLD+3HP vs. TLD alone. Design/methods: We analyzed data from an ongoing Phase 3 randomized trial com...

Background: Decentralised molecular testing for tuberculosis could reduce missed diagnoses and losses to follow-up in high-burden settings. The aim of this study was to evaluate the cost and cost-effectiveness of the Xpert Performance Evaluation for Linkage to Tuberculosis Care (XPEL-TB) study strategy, a multicomponent strategy including decentra...

Background: Lateral flow assays (LFAs) for the rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) provide an affordable, rapid and decentralised means for diagnosing coronavirus disease 2019 (COVID-19). Concentrating on urban areas in low- and middle-income countries, we examined whether ‘dynamic’ screening algorithms,...

The decisions made by stakeholders in the nation's health care system that affect the quality of care experienced by patients are too often made without the benefit of scientific evidence. A multidisciplinary set of investigators conducting health services research have traditionally filled this gap between research findings and clinical decision m...

Background Household contact investigation for people newly diagnosed with tuberculosis (TB) is poorly implemented, particularly in low- and middle-income countries. Conditional cash incentives may improve uptake. Methods We conducted a pragmatic, cluster randomized cross-over trial of two TB contact investigation approaches (household-based and i...

Background Diagnostic testing plays a critical role in the global COVID-19 response. Polymerase chain reaction (PCR) tests are highly accurate, but in resource-limited settings, limited capacity has led to testing delays; whereas lateral flow assays (LFAs) offer opportunities for rapid and affordable testing. We examined the potential epidemiologic...

Background Historically, the focus of cost-effectiveness analyses has been on the costs to operate and deliver interventions after their initial design and launch. The costs related to design and implementation of interventions have often been omitted. Ignoring these costs leads to an underestimation of the true price of interventions and biases ec...

Objectives Disease transmission models are used in impact assessment and economic evaluations of infectious disease prevention and treatment strategies, prominently so in the COVID-19 response. These models rarely consider dimensions of equity relating to the differential health burden between individuals and groups. We describe concepts and approa...

The degree to which individual heterogeneity in the production of secondary cases ("superspreading") affects tuberculosis (TB) transmission has not been systematically studied. We searched for population-based or surveillance studies in which whole genome sequencing was used to estimate TB transmission and the size distributions of putative TB tran...

99DOTS is a low-cost digital adherence technology that allows people with tuberculosis (TB) to self-report treatment adherence. There are limited data on its implementation, feasibility, and acceptability from sub-Saharan Africa. We conducted a longitudinal analysis and cross-sectional surveys nested within a stepped-wedge randomized trial at 18 he...

Purpose Interventions that can help streamline and reduce gaps in the tuberculosis (TB) care cascade can play crucial roles in TB prevention and care, but are often operationally complex and resource intensive, given the heterogenous settings in which they are implemented. In this study, we present a comparative analysis on cost-effectiveness of TB...

Fast Track models—in which patients coming to facility to pick up medications minimize waiting times through foregoing clinical review and collecting pre-packaged medications—present a potential strategy to reduce the burden of treatment. We examine effects of a Fast Track model (FT) in a real-world clinical HIV treatment program on retention to ca...

The COVID-19 pandemic has disrupted systems of care for infectious diseases—including tuberculosis—and has exposed pervasive inequities that have long marred efforts to combat these diseases. The resulting health disparities often intersect at the individual and community levels in ways that heighten vulnerability to tuberculosis. Effective respons...

Background The importance of finding people with undiagnosed tuberculosis (TB) hinges on their clinical and infectious trajectories. Assays for systematic screening should be optimized to find those whose TB will contribute most to future transmission or morbidity. Methods We constructed a mathematical model which tracks the disease trajectories o...

Background: Pre-exposure prophylaxis (PrEP) is a key component in helping to reduce HIV incidence in the United States. Long-acting injectable (LAI) PrEP is a new alternative to oral PrEP; its potential to impact local HIV epidemics remains unclear. Methods: The Johns Hopkins HIV Economic Epidemiological model (JHEEM) is a dynamic model of HIV t...

Background People living with HIV (PLHIV) have an increased risk of developing active tuberculosis (TB). To reduce the burden of TB among PLHIV, the World Health Organization (WHO) recommends systematic TB screening followed by (1) confirmatory TB testing for all who screen positive and (2) TB preventive therapy (TPT) for all TPT-eligible PLHIV who...

The annual risk of infection with Mycobacterium tuberculosis determines a population's exposure level and thus the fraction of incident tuberculosis resulting from recent infection (often considered as having occurred within the past 2 years). Contemporary annual risk of infection estimates centre around 1% in most high-burden countries. We present...

Introduction Mobile health (mHealth) applications may improve timely access to health services and improve patient-provider communication, but the upfront costs of implementation may be prohibitive, especially in resource-limited settings. Methods We measured the costs of developing and implementing an mHealth-facilitated, home-based strategy for...

Introduction Human-centred design (HCD) is a problem-solving approach that is increasingly used to develop new global health interventions. However, there is often a large initial cost associated with HCD, and global health decision-makers would benefit from an improved understanding of the cost-effectiveness of HCD, particularly the trade-offs bet...

Introduction: Health-related quality of life (HRQoL) is an important HIV outcome beyond viral suppression. However, there are limited data characterizing HRQoL of key populations, including female sex workers (FSW) living with HIV. Methods: We used baseline data (22 June 2018-23 March 2020) of FSW who were diagnosed with HIV and enrolled into a...

Background: Reductions in tuberculosis (TB) transmission have been instrumental in lowering TB incidence in the United States. Sustaining and augmenting these reductions are key public health priorities. Methods: We fit mechanistic transmission models to distributions of genotype clusters of TB cases reported to CDC during 2012-2016 in the Unite...