Maya Liv Petersen

University of California, Berkeley | UCB · School of Public Health

Introduction: Gaps in HIV RNA monitoring persist globally impeding the ability to determine clinical progress and outcomes. This study systematically evaluated provider (e.g., guideline non-adherence), system (e.g., laboratory error) and patient-based (e.g., refusal) drivers of missed viral load (VL) monitoring measurements among adults living with...

Many interventions are both beneficial to initiate and harmful to stop. Traditionally, to determine whether to deploy that intervention in a time-limited way depends on if, on average, the increase in the benefits of starting it outweigh the increase in the harms of stopping it. We propose a novel causal estimand that provides a more nuanced unders...

This manuscript explores the intersection of surrogate outcomes and adaptive designs in statistical research. While surrogate outcomes have long been studied for their potential to substitute long-term primary outcomes, current surrogate evaluation methods do not directly account for the potential benefits of using surrogate outcomes to adapt rando...

The Causal Roadmap outlines a systematic approach to asking and answering questions of cause and effect: define the quantity of interest, evaluate needed assumptions, conduct statistical estimation, and carefully interpret results. To protect research integrity, it is essential that the algorithm for statistical estimation and inference be prespeci...

The validity of medical studies based on real-world clinical data, such as observational studies, depends on critical assumptions necessary for drawing causal conclusions about medical interventions. Many published studies are flawed because they violate these assumptions and entail biases such as residual confounding, selection bias, and misalignm...

Introduction Identifying the optimal approaches to offering HIV prevention to meet the needs of those at risk is a high priority, particularly given the expanding toolkit of biomedical HIV prevention options. An ongoing study in rural East African communities evaluated the uptake of choices in product, testing mode and location of care delivery thr...

Illness narratives invite practitioners to understand how biomedical and traditional health information is incorporated, integrated, or otherwise internalized into a patient’s own sense of self and social identity. Such narratives also reveal cultural values, underlying patterns in society, and the overall life context of the narrator. Most illness...

Data on alcohol use and incident Tuberculosis (TB) infection are needed. In adults aged 15+ in rural Uganda (N=49,585), estimated risk of incident TB infection was 29.2% with alcohol use vs. 19.2% without (RR: 1.49; 95%CI: 1.40-1.60). There is potential for interventions to interrupt transmission among people who drink alcohol.

Polygamy is the practice of marriage to multiple partners. Approximately 6-11% of households in Uganda and 4-11% of households in Kenya are polygamous. The complex families produced by polygamous marriage customs give rise to additional considerations for healthcare providers and public health messaging around HIV care. Using 27 in-depth, semi-stru...

Understanding risk perception and risk-taking among youth can inform targeted prevention efforts. Using a health beliefs model-informed framework, we analysed 8 semi-structured, gender-specific focus group discussions with 93 youth 15–24 years old (48% male, 52% female), drawn from the SEARCH trial in rural Kenya and Uganda in 2017–2018, coinciding...

Background Pregnant and postpartum women in Sub-Saharan Africa are at high risk of HIV acquisition. We evaluated a person-centered dynamic choice intervention for HIV prevention (DCP) among women attending antenatal and postnatal care. Setting Rural Kenya and Uganda. Methods Women (aged 15 years or older) at risk of HIV acquisition seen at antena...

Background Consistent engagement in HIV treatment is needed for healthy outcomes, yet substantial loss-to-follow up persists, leading to increased morbidity, mortality and onward transmission risk. Although conditional cash transfers (CCTs) address structural barriers, recent findings suggest that incentive effects are time-limited, with cessation...

Strategic test allocation is important for control of both emerging and existing pandemics (eg, COVID-19, HIV). It supports effective epidemic control by (1) reducing transmission via identifying cases and (2) tracking outbreak dynamics to inform targeted interventions. However, infectious disease surveillance presents unique statistical challenges...

Background Human immunodeficiency virus (HIV) treatment reduces tuberculosis (TB) disease and mortality; however, the population-level impact of universal HIV-test-and-treat interventions on TB infection and transmission remain unclear. Methods In a sub-study nested in the SEARCH trial, a community cluster-randomized trial (NCT01864603), we assess...

Introduction Optimizing HIV prevention may require structured approaches for providing client‐centred choices as well as community‐based entry points and delivery. We evaluated the effect of a dynamic choice model for HIV prevention, delivered by community health workers (CHWs) with clinician support, on the use of biomedical prevention among perso...

Background Persons with HIV (PWH) with high mobility face obstacles to HIV care engagement and viral suppression. We sought to understand whether a patient-centered intervention for mobile PWH would improve viral suppression and retention in care, and if so, which subgroups would benefit most. Methods In a randomized trial, we evaluated the effect...

Introduction Unhealthy alcohol use significantly contributes to viral non‐suppression among persons with HIV (PWH). It is unknown whether brief behavioural interventions to reduce alcohol use can improve viral suppression among PWH with unhealthy alcohol use in sub‐Saharan Africa (SSA). Methods As part of the SEARCH study (NCT04810650), we conduct...

Introduction Innovative interventions are needed to improve HIV outcomes among adolescents and young adults (AYAs) living with HIV. Engaging AYAs in intervention development could increase effectiveness and youth acceptance, yet research is limited. We applied human-centred design (HCD) to refine adherence-support interventions pretrial and assesse...

Background Antiretroviral therapy (ART) assures major gains in health outcomes among people living with HIV, however, this benefit may not be realized by all due to care interruptions. Mobile populations comprise a subgroup that is likely to have sub-optimal care engagement, resulting in discontinuation of ART. We sought to evaluate the barriers to...

This document provides the statistical analytic plan (SAP) for a cluster randomized trial evaluating the effect of community-based Dynamic Choice HIV Prevention (DCP) intervention, delivered by community health workers in rural Uganda and Kenya (Clinicaltrials.gov: NCT04810650 ). The SAP was locked prior to unblinding and effect estimation.

Introduction: Human mobility is a critical aspect of existence and survival, but may compromise care engagement among people living with HIV (PLHIV). We examined the association between various forms of human mobility with retention in HIV care and antiretroviral treatment (ART) interruptions. Methods: In a cohort of adult PLHIV in Kenya and Uga...

Introduction Increasing interest in real-world evidence has fueled the development of study designs incorporating real-world data (RWD). Using the Causal Roadmap , we specify three designs to evaluate the difference in risk of major adverse cardiovascular events (MACE) with oral semaglutide versus standard-of-care: (1) the actual sequence of non-in...

Objective HIV prevention service delivery models that offer product choices, and the option to change preferences over time, may increase prevention coverage. Outpatient departments in sub-Saharan Africa diagnose a high proportion of new HIV infections, but are an understudied entry point to biomedical prevention. Design Individually randomized tr...

Increasing emphasis on the use of real-world evidence (RWE) to support clinical policy and regulatory decision-making has led to a proliferation of guidance, advice, and frameworks from regulatory agencies, academia, professional societies, and industry. A broad spectrum of studies use real-world data (RWD) to produce RWE, ranging from randomized t...

We present two novel approaches to variance estimation of semi-parametric efficient point estimators of the treatment-specific mean: (i) a robust approach that directly targets the variance of the influence function (IF) as a counterfactual mean outcome and (ii) a modified non-parametric bootstrap-based approach. The performance of these approaches...

Universal HIV testing and treatment (UTT) strategies aim to optimize population-level benefits of antiretroviral treatment. Between 2012 and 2018, four large community randomized trials were conducted in eastern and southern Africa. While their results were broadly consistent showing decreased population-level viremia reduces HIV incidence, it rema...

Introduction: Person-centred HIV prevention delivery models that offer structured choices in product, testing and visit location may increase coverage. However, data are lacking on the actual uptake of choices among persons at risk of HIV in southern Africa. In an ongoing randomized study (SEARCH; NCT04810650) in rural East Africa, we evaluated th...

San Francisco implemented one of the most intensive, comprehensive, multipronged COVID-19 pandemic responses in the United States using 4 core strategies: (1) aggressive mitigation measures to protect populations at risk for severe disease, (2) prioritization of resources in neighborhoods highly affected by COVID-19, (3) timely and adaptive data-dr...

The causal dose response curve is commonly selected as the statistical parameter of interest in studies where the goal is to understand the effect of a continuous exposure on an outcome.Most of the available methodology for statistical inference on the dose-response function in the continuous exposure setting requires strong parametric assumptions...

Across research disciplines, cluster randomized trials (CRTs) are commonly implemented to evaluate interventions delivered to groups of participants, such as communities and clinics. Despite advances in the design and analysis of CRTs, several challenges remain. First, there are many possible ways to specify the causal effect of interest (eg, at th...

Objective: Determine if patient-centered, streamlined HIV care achieves higher ART uptake and viral suppression than the standard treatment model for people with HIV (PWH) reporting hazardous alcohol use. Design: Community cluster-randomized trial. Methods: The SEARCH trial (NCT01864603) compared an intervention of annual population HIV testin...

Introduction: Increasing interest in real-world evidence has fueled the development of study designs incorporating real-world data (RWD). Using the Causal Roadmap, we specify three designs to evaluate the difference in risk of major adverse cardiovascular events (MACE) with oral semaglutide versus standard-of-care: 1) the actual sequence of non-inf...

Increasing emphasis on the use of real-world evidence (RWE) to support clinical policy and regulatory decision-making has led to a proliferation of guidance, advice, and frameworks from regulatory agencies, academia, professional societies, and industry. A broad spectrum of studies use real-world data (RWD) to produce RWE, ranging from randomized c...

Causal mediation analysis with random interventions has become an area of significant interest for understanding time-varying effects with longitudinal and survival outcomes. To tackle causal and statistical challenges due to the complex longitudinal data structure with time-varying confounders, competing risks, and informative censoring, there exi...

Objectives To identify incident SARS-CoV-2 infections and inform effective mitigation strategies in university settings, we piloted an integrated symptom and exposure monitoring and testing system among a cohort of university students and employees. Design Prospective cohort study. Setting A public university in California from June to August 202...

The Hazard Ratio (HR) is a well-established treatment effect measure in randomized trials involving right-censored time-to-events, and the Cardiovascular Outcome Trials (CVOTs) conducted since the FDA’s 2008 guidance have indeed largely evaluated excess risk by estimating a Cox HR. On the other hand, the limitations of the Cox model and of the HR a...

Background: Optimizing retention in human immunodeficiency virus (HIV) treatment may require sequential behavioral interventions based on patients' response. Methods: In a sequential multiple assignment randomized trial in Kenya, we randomly assigned adults initiating HIV treatment to standard of care (SOC), Short Message Service (SMS) messages,...

COVID-19 oral treatments require initiation within 5 days of symptom onset. Although antigen tests are less sensitive than RT-PCR, rapid results could facilitate entry to treatment. We collected anterior nasal swabs for BinaxNOW and RT-PCR testing and clinical data at a walk-up, community site in San Francisco, California between January and June 2...

Introduction: Switch to dolutegravir (DTG) in treatment-experienced people living with HIV (PLH) is associated with excess weight gain in some settings; data are limited from rural low-income settings with low obesity prevalence. Methods: In rural Kenya, we conducted a retrospective cohort study at eight HIV clinics and a single-site prospective...

Background: Adolescents and young adults living with HIV (AYAH) aged 14-24 years in Africa experience substantially higher rates of virological failure and HIV-related mortality than adults. We propose to utilize developmentally appropriate interventions with high potential for effectiveness, tailored by AYAH pre-implementation, in a sequential mu...

Background Four large community-randomized trials examining universal testing and treatment (UTT) to reduce HIV transmission were conducted between 2012–2018 in Botswana, Kenya, Uganda, Zambia and South Africa. In 2014, the UNAIDS 90–90-90 targets were adopted as a useful metric to monitor coverage. We systematically review the approaches used by t...

Strategic test allocation plays a major role in the control of both emerging and existing pandemics (e.g., COVID-19, HIV). Widespread testing supports effective epidemic control by (1) reducing transmission via identifying cases, and (2) tracking outbreak dynamics to inform targeted interventions. However, infectious disease surveillance presents u...

Personalized intervention strategies, in particular those that modify treatment based on a participant's own response, are a core component of precision medicine approaches. Sequential Multiple Assignment Randomized Trials (SMARTs) are growing in popularity and are specifically designed to facilitate the evaluation of sequential adaptive strategies...

In biomedical science, analyzing treatment effect heterogeneity plays an essential role in assisting personalized medicine. The main goals of analyzing treatment effect heterogeneity include estimating treatment effects in clinically relevant subgroups and predicting whether a patient subpopulation might benefit from a particular treatment. Convent...

Background Fewer than 10% of people with hypertension in sub-Saharan Africa are diagnosed, linked to care, and achieve hypertension control. We hypothesized that a one-time financial incentive and phone call reminder for missed appointments would increase linkage to hypertension care following community-based screening in rural Uganda and Kenya. M...

In biomedical science, analyzing treatment effect heterogeneity plays an essential role in assisting personalized medicine. The main goals of analyzing treatment effect heterogeneity include estimating treatment effects in clinically relevant subgroups and predicting whether a patient subpopulation might benefit from a particular treatment. Convent...

Objective To evaluate implementation of a community-engaged approach to scale up COVID-19 mass testing in low-income, majority-Latino communities. Methods In January 2021, we formed a community-academic “Latino COVID-19 Collaborative” with residents, leaders, and community-based organizations (CBOs) from majority-Latinx, low-income communities in...

Augmenting the control arm of a randomized controlled trial (RCT) with external data may increase power but at the risk of introducing bias. Existing methods for combining data sources generally rely on stringent assumptions or may have decreased coverage or power in the presence of bias. We present a novel approach to the integration of RCT and re...

Personalized intervention strategies, in particular those that modify treatment based on a participant's own response, are a core component of precision medicine approaches. Sequential Multiple Assignment Randomized Trials (SMARTs) are growing in popularity and are specifically designed to facilitate the evaluation of sequential adaptive strategies...

Pre-exposure prophylaxis (PrEP) implementation is underway across sub-Saharan Africa. However, little is known about health care providers' experiences with PrEP provision in generalized epidemic settings, particularly outside of selected risk groups. In this study (NCT01864603), universal access to PrEP was offered to adolescents and adults at ele...

Importance: Characterizing the clinical symptoms and evolution of community-based SARS-CoV-2 infections may inform health practitioners and public health officials in a rapidly changing landscape of population immunity and viral variants. Objectives: To compare COVID-19 symptoms among people testing positive with a rapid antigen test (RAT) durin...

Background Social network analysis can elucidate Tuberculosis (TB) transmission dynamics outside of the home and may inform novel network-based case-finding strategies. Methods We assessed the association between social network characteristics and prevalent TB infection among residents (≥15 years) of 9 rural communities in Eastern Uganda. Social c...

Background. COVID-19 oral treatments require initiation within 5 days of symptom onset. Although antigen tests are less sensitive than RT-PCR, rapid results could facilitate entry to treatment. As SARS-CoV-2 variants and host immunity evolve, it is important to characterize the use case for rapid antigen tests for treatment entry. Methods. We colle...

Introduction Until vaccines became available in late 2020, our ability to prevent the spread of COVID-19 within countries depended largely on voluntary adherence to mitigation measures. However, individual decision-making regarding acceptable COVID-19 risk is complex. To better understand decision-making regarding COVID-19 risk, we conducted a qual...

The Sustainable East Africa Research in Community Health (SEARCH) trial was a universal test-and-treat (UTT) trial in rural Uganda and Kenya, aiming to lower regional HIV-1 incidence. Here, we quantify breakthrough HIV-1 transmissions occurring during the trial from population-based, dried blood spot samples. Between 2013 and 2017, we obtained 549...

Given an (optimal) dynamic treatment rule, it may be of interest to evaluate that rule – that is, to ask the causal question: what is the expected outcome had every subject received treatment according to that rule? In this paper, we study the performance of estimators that approximate the true value of: (1) an a priori known dynamic treatment rule...

The optimal dynamic treatment rule (ODTR) framework offers an approach for understanding which kinds of patients respond best to specific treatments – in other words, treatment effect heterogeneity. Recently, there has been a proliferation of methods for estimating the ODTR. One such method is an extension of the SuperLearner algorithm – an ensembl...

Importance: Community-based COVID-19 testing and vaccination programs play a crucial role in mitigating racial and ethnic disparities in COVID-19 service delivery. They also represent a platform that can be leveraged to expand access to testing for chronic diseases, including diabetes, that disproportionately affect the Latinx community and other...

Importance Characterizing clinical symptoms and evolution of community-based SARS Co-V-2 infections can inform health practitioners and public health officials in a rapidly changing landscape of population immunity and viral variants. Objective To characterize COVID-19 symptoms during the Omicron period compared to pre-Delta and Delta variant peri...

Youth living with HIV in sub-Saharan Africa have poor HIV care outcomes. We determined the association of recent significant life-events with HIV antiretroviral treatment (ART) initiation and HIV viral suppression in youth aged 15–24 years living with HIV in rural Kenya and Uganda. This was a cross-sectional analysis of 995 youth enrolled in the SE...

Background Approaches that allow easy access to pre-exposure prophylaxis (PrEP), such as over-the-counter provision at pharmacies, could facilitate risk-informed PrEP use and lead to lower HIV incidence, but their cost-effectiveness is unknown. We aimed to evaluate conditions under which risk-informed PrEP use is cost-effective. Methods We applied...

We found no significant difference in cycle threshold values between vaccinated and unvaccinated persons infected with SARS-CoV-2 Delta, overall or stratified by symptoms. Given the substantial proportion of asymptomatic vaccine breakthrough cases with high viral levels, interventions, including masking and testing, should be considered in settings...

Background: SARS-CoV-2 rapid antigen tests are an important public health tool. Objective: To evaluate field performance of the BinaxNOW rapid antigen test (Abbott) compared with reverse transcriptase polymerase chain reaction (RT-PCR) for detecting infection with the Omicron variant of SARS-CoV-2. Design: Cross-sectional surveillance study....

Growing literature has shown heterogenous effects of conditional cash incentives (CCIs) on HIV care retention. The field lacks insights into reasons why incentives impact various patients in different ways–differences that may be due to variations in psychological and social mechanisms of effect. A deeper understanding of patients’ perceptions and...

While SARS-CoV-2 vaccines prevent severe disease effectively, post-vaccination ‘breakthrough’ COVID-19 infections and transmission among vaccinated individuals remain ongoing concerns. We present an in-depth characterization of transmission and immunity among vaccinated individuals in a household, revealing complex dynamics and unappreciated comorb...

In 731 persons seeking COVID-19 testing at a walk-up San Francisco community site in January 2022, simultaneous nasal rapid antigen testing (BinaxNOWTM) and RT-PCR testing was performed. There were 296 (40.5%) positive tests by RT-PCR; 97% of a random sample were the omicron variant. Sensitivity of a single antigen test was 95.2% (95% CI 92-98%); 8...

The wide spectrum of SARS-CoV-2 variants with phenotypes impacting transmission and antibody sensitivity necessitates investigation of the immune response to different spike protein versions. Here, we compare the neutralization of variants of concern, including B.1.617.2 (Delta) and B.1.1.529 (Omicron) in sera from individuals exposed to variant in...

Background Universal testing and treatment for HIV has shown promise as an approach to reduce mortality and lower HIV incidence. Evidence on the economic effects of this approach on individuals and households in low-resource settings is scarce. We aimed to examine the effect of universal HIV testing and treatment on a range of economic outcomes. M...