About

Omar Galárraga is a health economist and health services researcher with a PhD from Johns Hopkins University obtained in 2007. He is a tenured Professor of Health Services Policy and Practice at Brown University School of Public Health and serves as the Director of the Center for Global Public Health (CGPH). His research focuses on using insights from health and behavioral economics to address issues related to HIV treatment and prevention, health systems, and applied health econometric analysis. He evaluates economic-based interventions through experimental and rigorous non-experimental methods, contributing to over 160 publications in health economics, public health, and health services research journals. Galárraga's work includes serving as Multiple Principal Investigator on NIH-funded projects that examine the impact of prescription caps on health outcomes in people with HIV, the effectiveness of financial incentives for physical activity, and integrated community-based HIV and non-communicable disease care models in Kenya. He has held various leadership roles, including serving on advisory committees for the Office of AIDS Research, the Population Studies & Training Center, the Center for Latin American Studies, and the Data Science Institute. He is also involved in organizing the 17th World Congress of the International Health Economics Association scheduled for 2027. His research is conducted in multiple countries including Ecuador, China, Ghana, Kenya, Mexico, South Africa, and the United States, often in collaboration with community and academic partners.

Research topics

• Family medicine
• Medicine
• Nursing
• Psychiatry
• Psychology
• Environmental health
• Social psychology
• Developmental psychology
• Internal medicine

Selected publications

• The Best Health for the Most People for the Least Cost.

  PubMed · 2026-04-01

  article1st authorCorresponding

  This article: (1) summarizes the accomplishments of the Center for Global Public Health (CGPH) at the Brown University School of Public Health, with a focus on the Center's work over the first decade following the School of Public Health's accreditation (2013-2023); and (2) provides a vision for the Center's future. Select research studies are highlighted throughout the article as examples of the Center's approaches to public health leadership and global partnerships.

  Publisher

• Cost-Effectiveness of Using Conditional Economic Incentives to Improve Pre-exposure Prophylaxis Adherence Among Male Sex Workers

  PharmacoEconomics - Open · 2025-04-09 · 2 citations

  articleOpen accessSenior author

  INTRODUCTION: Conditional economic incentives can improve medication-taking behaviors among populations at risk of contracting human immunodeficiency virus (HIV). However, there are no data on the cost-effectiveness of incentive programs for improving pre-exposure prophylaxis (PrEP) adherence among male sex workers (MSWs) who have one of the highest HIV acquisition rates. Our objective was to assess the cost-effectiveness of incentive programs to improve adherence to pre-exposure prophylaxis (PrEP) among male sex workers METHODS: We conducted an economic evaluation of the PrEP Seguro randomized pilot trial in Mexico (ClinicalTrials.gov: NCT03674983). Among n = 110 MSWs, those randomized to the intervention received tiered incentives based on PrEP drug levels in scalp hair measured at three clinic visits over 6 months. The intervention led to a 28.7% increase in scalp hair PrEP concentration, consistent with increased adherence (p = 0.05). Here we use a micro-costing approach from the health system perspective to calculate costs. Quality-adjusted life years (QALYs) were estimated from the number of HIV infections averted through sufficient PrEP adherence (tenofovir concentration > 0.011 ng/mg corresponding to greater than or equal to three weekly doses). Incremental cost-effectiveness ratios (ICERs) estimated the cost/QALY gained owing to the intervention. RESULTS: The mean cost per patient was US $165.53 and $179.55 among standard care and incentive patients, respectively. Over 6 months of follow-up, 62% of standard care patients and 78% of incentive recipients were PrEP adherent. After the program, the lifetime average QALYs gained per infection avoided were 9.17 (minimum, maximum: 7.5, 10.8) and 9.84 (minimum, maximum: 8.05, 11.6) among standard care and incentive patients, respectively. The 6-month ICER was US $20.92/QALY gained by the intervention, which was highly cost-effective at a willingness-to-pay of US $8655 (Mexico's 2020 per capita gross domestic product (GDP)). DISCUSSION: Using behavioral economics approaches for enhancing adherence to HIV prevention may offer health and fiscal benefits through reduced HIV incidence. Fully powered implementation trials can determine future cost-effectiveness of scaling up incentives for PrEP adherence among high-risk populations.

  PublisherOA PDFDOI

• Demographic shifts and aging in the middle of the world: health challenges and policy opportunities in Ecuador

  The Gerontologist · 2025-07-28 · 3 citations

  review

  Ecuador is a middle-income country in South America with approximately 18 million residents. While still young, the country is undergoing a demographic shift that has led to an aging population. The percent of adults aged 65 and above is projected to increase from 7.84% in 2022 to nearly 18% by 2050. This transformation presents substantial challenges that require social and policy solutions. Gerontological research in Ecuador has largely emphasized biomedical science. National datasets, including the Survey of Health, Welfare, and Aging (SABE), the National Health and Nutrition Survey (ENSANUT), and the Atahualpa Project, have provided valuable insights into population health. However, gaps remain due to the absence of national and longitudinal data that capture the population subgroups that call Ecuador their home. We conclude by emphasizing the need to address national issues such as: ensuring social security coverage, strengthening poverty alleviation programs, and improving access to healthcare. By addressing these issues, Ecuador will be better equipped to meet the evolving needs of its aging population.

  PublisherDOI

• Is membership in microfinance initiatives associated with viral load suppression among HIV patients? Evidence from western Kenya

  BMC Global and Public Health · 2025-06-25 · 1 citations

  articleOpen accessSenior author

  BACKGROUND: Social and economic factors have considerable influence on the lives of people living with HIV (PLHIV). These factors shape their health behaviors, willingness to engage with other members of their communities for support, and ability to seek appropriate and timely treatment options. Evidence has shown that microfinance initiatives, by providing access to credit and social networks, have the potential to help PLHIV overcome some of these barriers. The objective of this study was to understand the association between microfinance membership and viral load suppression among HIV patients. METHODS: We used data from the Academic Model Providing Access to Healthcare (AMPATH)-Kenya's Group Integrated Savings for Health Empowerment (GISHE), a microfinance initiative (MFI), to study the association between GISHE participation and viral load suppression. Our longitudinal dataset consisted of a matched group of 3609 HIV patients. We examined the association between GISHE membership and viral load suppression by addressing the missing data problem with respect to the viral load count via multiple imputation. RESULTS: Our study revealed that GISHE membership was associated with increased viral load suppression (adjusted odds ratio (AOR) = 1.15; 95% confidence interval (CI), 1.03-1.29). Further, the study found that male patients were less likely to be virally suppressed (AOR = 0.85; 95% CI, 0.74-0.97), as were the patients in the most advanced disease stage (AOR = 0.71; 95% CI, 0.52-0.95). The finding that GISHE participation was associated with a greater likelihood of viral load suppression held even after addressing the missing data problem. CONCLUSIONS: We conclude that GISHE-type programs hold promise as scalable interventions to combat HIV/AIDS in Kenya and other countries where the disease is a generalized epidemic.

  PublisherOA PDFDOI

• Overcoming the HIV Pre-exposure Prophylaxis Uptake Barrier with Health Action Process Approach and Conditional Economic Incentives among Men Who Have Sex with Men in three Chinese cities: Protocol for a Randomized Controlled Trial (Preprint)

  2025-08-11

  preprintOpen access

  <sec> <title>BACKGROUND</title> Despite high pre-exposure prophylaxis (PrEP) awareness and willingness among Chinese men who have sex with men (MSM), actual uptake remains critically low. This intention-behavior gap significantly hinders Human Immunodeficiency Virus (HIV) prevention efforts. </sec> <sec> <title>OBJECTIVE</title> This randomized controlled trial evaluates the effectiveness of Health Action Process Approach (HAPA) -driven interventions to enhance PrEP initiation and adherence in this high-risk population. </sec> <sec> <title>METHODS</title> High-risk HIV-negative MSM naive to PrEP will be recruited via community-based organizations. Participants will undergo individual randomization to three arms: (1) HAPA-based behavioral intervention featuring tailored WeChat messages and two structured motivational interviews targeting stage-specific barriers; (2) Combined HAPA intervention with group-based conditional economic incentives (GCEI) linked to peer group initiation rates, incorporating facilitated offline group activities; or (3) Standard care control. The physician-prescribed PrEP initiation rate at three months serves as primary outcome. Secondary outcomes include PrEP adherence, HIV risk perception, PrEP-related stigma, and intervention acceptability. Analysis will follow intention-to-treat principles using mixed-effects models. </sec> <sec> <title>RESULTS</title> . </sec> <sec> <title>CONCLUSIONS</title> This study rigorously tests a novel intervention integrating the HAPA–targeting distinct motivational and volitional phases of PrEP use–with a GCEI model leveraging peer influence. By addressing both individual cognitive-behavioral barriers and financial disincentives within a supportive group context, this approach offers a potentially scalable strategy to bridge the PrEP uptake gap in China. Findings will provide critical evidence on the added value of combining theory-driven behavioral techniques with peer-group economic incentives for HIV prevention. </sec> <sec> <title>CLINICALTRIAL</title> This study was registered at ClinicalTrials.gov (NCT06931106). </sec>

  PublisherDOI

• Incentivizing Adherence to Gender-Affirming PrEP Programs: A Stated Preference Discrete-Choice Experiment among Transgender and Gender Nonbinary Adults

  Medical Decision Making · 2025-08-16 · 1 citations

  articleSenior author

  ObjectivesTransgender (trans) people have disproportionately high HIV risk, yet adherence to preexposure prophylaxis (PrEP) remains low in this population. We aimed to determine which factors matter most in the decision of HIV-negative transgender adults to adhere to long-acting injectable PrEP (LA-PrEP), and the acceptability of providing incentives conditional on LA-PrEP program engagement.MethodsFrom March to April 2023, 385 trans adults in Washington State completed a discrete-choice experiment (DCE) eliciting preferences for a conditional economic incentive program that would provide free LA-PrEP and gender-affirming care during bimonthly visits. We used the best-best preference elicitation method across 2 hypothetical programs with an opt-out option. Program attributes included incentive format and amount, method for determining PrEP adherence, and type of hormone co-prescription. We used a rank-ordered mixed logit model for main results and estimated respondents' marginal willingness to accept each program attribute. We plotted the probability of choosing an incentivized LA-PrEP program over a range of respondent characteristics.ResultsThe optimal program design would 1) deliver incentives in cash, 2) confirm PrEP adherence via blood testing, 3) provide counseling in person, and 4) provide prescriptions for injectable gender-affirming hormones. From a maximum incentive amount of $1,200/year, respondents were willing to forgo up to $689 to receive incentives in cash (instead of voucher) and up to $547 to receive injectable (instead of oral) hormones. The probability of choosing a hypothetical program over no program waned as adults aged (>40 y) and as income increased (>$75,000/y).ConclusionsConditional economic incentives are likely acceptable and effective for improving LA-PrEP adherence, especially among younger trans adults with fewer financial resources. A randomized trial is needed to confirm the DCE's validity for predicting actual program uptake.HighlightsGender-related stigma, economic barriers, and medical concerns about hormone interactions can keep transgender (trans) adults from engaging in HIV prevention behaviors.Combining gender-affirming care with conditional economic incentives may help reduce present bias and increase trans persons' motivation to adhere to long-acting injectable preexposure prophylaxis (LA-PrEP).From a maximum yearly incentive of $1,200, trans discrete-choice experiment respondents were willing to forgo up to $689 to receive a cash (rather than voucher) incentive and up to $547 to receive co-prescriptions for injectable (rather than oral) hormones as part of a hypothetical HIV prevention program.The probability of choosing an LA-PrEP program over no program begins to wane as adults age (>40 y) and as annual income increases (>$75,000/year), such that incentivized LA-PrEP programs may be especially salient for younger trans adults with fewer financial resources.

  PublisherDOI

• Cost-Effectiveness of an Enhanced Patient Care Intervention for Improving Viral Suppression Among Kenyan Adults Living With HIV

  Value in Health Regional Issues · 2025-05-21 · 1 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• Adaptation, acceptability and preliminary impacts of a sexual health and financial literacy intervention for indigenous adolescents in Ecuador: A mixed-methods pilot study

  Public Health · 2025-12-08

  articleOpen accessSenior author

  OBJECTIVES: To assess the acceptability, feasibility and preliminary impacts of a group-based financial literacy and reproductive health intervention adapted for indigenous youth in Ecuador. STUDY DESIGN: Mixed-methods quasi-experimental pilot study. METHODS: This study (November 2023-June 2024) enrolled 47 adolescents, ages 15-19, from Cotacachi, Ecuador. Using the ADAPT-ITT framework, we adapted an existing entrepreneurship curriculum to the local context, and integrated curriculum with an existing reproductive health education platform. Twenty-nine adolescents received the school-based group intervention over 4 months, with 18 control participants. Qualitatively, focus groups elicited intervention acceptability from 11 youth. Quantitatively, Wilcoxon rank-sum tests and MANOVA compared empowerment and health outcomes between intervention participants and controls. Adjusted linear and logistic regression estimated intention-to-treat effects of the intervention on outcomes. RESULTS: The study recruited 96.7 % and 60.0 % of the target sample for the intervention (29/30) and control (18/30) conditions, respectively. Regression results showed positive associations between the intervention and financial literacy (β = 1.33, p < 0.01) and sexual health knowledge (β = 1.52, p < 0.01), and modest positive associations (p > 0.10) with entrepreneurial self-efficacy, engagement in income-generating activities, gender empowerment, and less-frequent penetrative sex. All focus group participants valued the financial management and entrepreneurship components of the intervention; most stated that the curriculum improved their decision-making around sex and relationships. CONCLUSIONS: This pilot evidence supports acceptability and potential benefits of an economic empowerment and reproductive health intervention for indigenous youth at high risk of pregnancy in Ecuador. A randomized trial is needed to test the effectiveness of the intervention on longer-term income generation and pregnancy reduction.

  PublisherDOI

• A Cost-Effectiveness Analysis of Rivaroxaban Compared to Warfarin for the Management of Venous Thromboembolism in Western Kenya

  Clinical Drug Investigation · 2025-06-28 · 2 citations

  articleOpen access

  BACKGROUND AND OBJECTIVE: Access to direct oral anticoagulants (DOACs) in sub-Saharan Africa is limited due to prohibitive upfront costs, making warfarin the standard of care for many patients, especially those relying on public-sector healthcare. This study evaluated the cost-effectiveness of using the DOAC, rivaroxaban, compared to warfarin for treating venous thromboembolism (VTE), a cardiovascular disorder caused by blood clots in the veins, in western Kenya. METHODS: We developed a discrete-time individual state-transition Markov model to simulate a VTE patient's quality-adjusted life-years (QALYs) and annual treatment costs under a rivaroxaban or warfarin therapy strategy. Transition state probabilities were derived from real-world event-rate data observed in patients treated with rivaroxaban (n = 160) or warfarin (n = 116) for VTE at Moi Teaching and Referral Hospital in western Kenya. Base-case parameter values were obtained from cohort event rates, local costs, and literature-derived utility values. Cost-effectiveness was assessed over a 1-year time horizon using an incremental cost-effectiveness ratio (ICER) threshold of (US)$6020.40 per QALY gained (equivalent to three times Kenya's 2021 per capita GDP). Deterministic and probabilistic sensitivity analyses were conducted to assess parameter and model uncertainty. RESULTS: After 12 months, total mean treatment costs per patient were $216.00 and $173.00 using warfarin and rivaroxaban, respectively. In the base-case analysis, rivaroxaban therapy resulted in an additional 0.023 QALYs per patient compared to warfarin, with an ICER of $- 1862.00 per QALY gained. Based on probabilistic sensitivity analysis with Monte Carlo simulation, when costs, utility values, and event rates were varied, rivaroxaban was cost-effective compared to warfarin in 84.1% of all simulations at a willingness-to-pay threshold of $6020.40 per QALY. One-way sensitivity analyses and scenario analyses were stable with rivaroxaban therapy, resulting in fewer costs and higher QALYs. CONCLUSIONS: In this study, rivaroxaban is a clinically and economically superior alternative to warfarin. This research may catalyze further discussions with policymakers and industry partners to scale up the appropriate use of rivaroxaban in resource-constrained settings.

  PublisherOA PDFDOI

• Association Between Medicaid Prescription Drug Caps And Antiretroviral Adherence Among People Living With HIV

  Health Affairs · 2025-12-01 · 1 citations

  articleOpen access

  To control spending, some state Medicaid agencies "cap" the number of prescriptions that a beneficiary can fill each month, presenting a potential barrier to medication adherence for people with chronic health conditions. To evaluate the association between Medicaid prescription drug cap policies and antiretroviral therapy (ART) adherence among people living with HIV, we compared beneficiaries in four states with caps to beneficiaries in eight states without caps during the period 2016-19. In three of four cap states, cap status was associated with a 9 percent relative reduction in the percentage of days covered by ART over the course of twelve months compared to noncap states, and a 24 percent relative reduction in the likelihood of achieving optimal ART adherence (90 percent or higher) over the course of twelve months. The association was stronger for people with higher baseline ART adherence or more baseline comorbidities. We also identified racial and ethnic disparities, where the magnitude of ART adherence reduction associated with caps was significantly greater for Black and Hispanic people than for White people. Medicaid prescription drug cap policies appear to be both a potential source of racial and ethnic disparity and an impediment to achieving clinical targets for optimal ART adherence among people with HIV.

  PublisherOA PDFDOI

Frequent coauthors

• Sandra G. Sosa‐Rubí

  Instituto Nacional de Salud Pública

  324 shared

• Richard G. Wamai

  Northeastern University

  251 shared

• Sergio Bautista‐Arredondo

  Secretaria de Salud

  238 shared

• Joseph Wang’ombe

  University of Nairobi

  235 shared

• Neil Martinson

  Perinatal HIV Research Unit

  234 shared

• Claire Chaumont

  232 shared

• Ada Kwan

  232 shared

• Felix Masiye

  University of Zambia

  231 shared

Education

• Ph.D.

  Johns Hopkins University

  2007