Warren B. Bilker
VerifiedUniversity of Pennsylvania · Rehabilitation Medicine
Active 1992–2026
About
Warren B. Bilker, Ph.D., is a Professor of Biostatistics in the Department of Biostatistics and Epidemiology at the Hospital of the University of Pennsylvania. He is a member of the Epidemiology and Biostatistics Graduate Group within the Biomedical Graduate Studies at the University of Pennsylvania School of Medicine. Dr. Bilker also serves as a Senior Scholar at the Center for Clinical Epidemiology and Biostatistics at the same institution and is the Faculty Co-director of the Biostatistics Analysis Center (BAC). His educational background includes a B.A. in Mathematics and an M.S. in Statistics from Temple University, and a Ph.D. in Biostatistics from Johns Hopkins University. His research expertise focuses on biostatistics, with numerous publications in areas such as clinical epidemiology, pain management, opioid use, and infectious diseases. Dr. Bilker's work involves analyzing predictors of treatment response, opioid withdrawal symptoms, trends in medication use, and risk factors for infections, contributing significantly to the field of biostatistics and epidemiology.
Research topics
- Medicine
- Internal medicine
- Neuroscience
- Psychology
- Microbiology
- Developmental psychology
- Audiology
- Cognitive psychology
Selected publications
British Journal of Clinical Pharmacology · 2026-05-03
articleOpen accessAIM: A prior non-randomized study suggests that potassium supplementation may improve survival among furosemide initiators, and a randomized trial suggests that salt substitutes containing potassium might lower stroke risk. We conducted a retrospective cohort study using health-care data to confirm or refute these associations among new users of furosemide. METHODS: The exposure of interest was empiric potassium dispensing (yes/no) concurrent with furosemide initiation. Outcomes were all-cause mortality, sudden cardiac arrest/ventricular arrhythmia (SCA/VA), and stroke. Primary as-started and secondary as-treated analyses were performed with Cox proportional hazards regression. We used inverse probability of treatment weighting (IPTW) to control for confounding, with weights calculated from high-dimensional propensity scores. RESULTS: We identified 511 462 and 320 703 initiators of furosemide <40 and ≥40 mg/day with 21.5% and 35.3%, respectively, starting empiric potassium supplementation. In initiators of furosemide <40 mg/day with (vs. without) empiric potassium, as-started IPTW-hazard ratios (HRs) were 1.02 (95%CI 1.01-1.04) for death, 1.00 (0.94-1.04) for SCA/VA, and 1.03 (1.00-1.06) for stroke. Similarly, in initiators of furosemide ≥40 mg/day with (vs. without) empiric potassium, as-started IPTW-HRs were 1.02 (1.00-1.03) for death, 0.98 (0.94-1.03) for SCA/VA, and 1.01 (0.98-1.04) for stroke. CONCLUSION: We did not observe associations suggesting a clinically meaningful effect of empiric potassium supplementation among furosemide users. However, given the high prevalence of furosemide use among highly heterogeneous patient populations, a large pragmatic trial may be warranted to more definitively evaluate the potential benefits and harms of empiric potassium supplementation among furosemide initiators.
UNC Libraries · 2026-02-13
articleOpen accessBackground People living with HIV (PLWH) make up a significant proportion of the population in sub-Saharan Africa, and there exists a significant gap in research on the burden and associated risk factors for extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) in this population. We describe the risk factors associated with ESCrE colonization in nonhospitalized PLWH. Methods This is a secondary data analysis of nonhospitalized adult PLWH included in a regional surveillance cohort study describing colonization with ESCrE in Botswana. Participants underwent rectal swab sampling to identify ESCrE. Bivariate and multivariable analysis was used to determine risk factors associated with ESCrE colonization. Results A total of 546 adult PLWH were recruited over 3 districts and were included in this analysis. The mean (standard deviation) age was 42 (10.4) years, and 448 (82.1%) were women. Our findings demonstrated that 27.3% (149/546) of participants screened positive for ESCrE rectal colonization. Independent risk factors {adjusted odds ratio (aOR) [95% CI]} for ESCrE colonization included recent hospitalization (3.37 [1.13–9.98]), at least 1 household member with ESCrE colonization (1.74 [1.01–3.00]), and recruitment before the countrywide COVID-19 lockdown (2.01 [1.33–3.04]). Recent antibiotic use had an elevated OR for ESCrE colonization that did not achieve statistical significance in the adjusted analysis (aOR: 1.84 [.92–3.68]). Conclusions Hospitalization and colonization of other household members with ESCrE are important factors associated with colonization with ESCrE, as seen in other populations. The prevalence of ESCrE following the COVID-19 lockdown was significantly lower, suggesting the presence of factors that were protective against colonization. It is unclear how long these effects lasted.
Open Forum Infectious Diseases · 2026-01-24
articleOpen accessBackground: People living with HIV (PLWH) make up a significant proportion of the population in sub-Saharan Africa, and there exists a significant gap in research on the burden and associated risk factors for extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) in this population. We describe the risk factors associated with ESCrE colonization in nonhospitalized PLWH. Methods: This is a secondary data analysis of nonhospitalized adult PLWH included in a regional surveillance cohort study describing colonization with ESCrE in Botswana. Participants underwent rectal swab sampling to identify ESCrE. Bivariate and multivariable analysis was used to determine risk factors associated with ESCrE colonization. Results: A total of 546 adult PLWH were recruited over 3 districts and were included in this analysis. The mean (standard deviation) age was 42 (10.4) years, and 448 (82.1%) were women. Our findings demonstrated that 27.3% (149/546) of participants screened positive for ESCrE rectal colonization. Independent risk factors {adjusted odds ratio (aOR) [95% CI]} for ESCrE colonization included recent hospitalization (3.37 [1.13-9.98]), at least 1 household member with ESCrE colonization (1.74 [1.01-3.00]), and recruitment before the countrywide COVID-19 lockdown (2.01 [1.33-3.04]). Recent antibiotic use had an elevated OR for ESCrE colonization that did not achieve statistical significance in the adjusted analysis (aOR: 1.84 [.92-3.68]). Conclusions: Hospitalization and colonization of other household members with ESCrE are important factors associated with colonization with ESCrE, as seen in other populations. The prevalence of ESCrE following the COVID-19 lockdown was significantly lower, suggesting the presence of factors that were protective against colonization. It is unclear how long these effects lasted.
Risk Factors for Community Colonization With Extended-Spectrum Cephalosporin-Resistant Enterobacterales Among People Living With HIV in Botswana
Open MIND · 2026-01-01
articleBackground People living with HIV (PLWH) make up a significant proportion of the population in sub-Saharan Africa, and there exists a significant gap in research on the burden and associated risk factors for extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) in this population. We describe the risk factors associated with ESCrE colonization in nonhospitalized PLWH. Methods This is a secondary data analysis of nonhospitalized adult PLWH included in a regional surveillance cohort study describing colonization with ESCrE in Botswana. Participants underwent rectal swab sampling to identify ESCrE. Bivariate and multivariable analysis was used to determine risk factors associated with ESCrE colonization. Results A total of 546 adult PLWH were recruited over 3 districts and were included in this analysis. The mean (standard deviation) age was 42 (10.4) years, and 448 (82.1%) were women. Our findings demonstrated that 27.3% (149/546) of participants screened positive for ESCrE rectal colonization. Independent risk factors {adjusted odds ratio (aOR) [95% CI]} for ESCrE colonization included recent hospitalization (3.37 [1.13–9.98]), at least 1 household member with ESCrE colonization (1.74 [1.01–3.00]), and recruitment before the countrywide COVID-19 lockdown (2.01 [1.33–3.04]). Recent antibiotic use had an elevated OR for ESCrE colonization that did not achieve statistical significance in the adjusted analysis (aOR: 1.84 [.92–3.68]). Conclusions Hospitalization and colonization of other household members with ESCrE are important factors associated with colonization with ESCrE, as seen in other populations. The prevalence of ESCrE following the COVID-19 lockdown was significantly lower, suggesting the presence of factors that were protective against colonization. It is unclear how long these effects lasted.
BMJ Open · 2026-03-01
articleOpen accessINTRODUCTION: -adjuvanted respiratory syncytial virus (RSV) prefusion F protein-based vaccine (adjuvanted RSVPreF3) for adults aged ≥60 years. The approval was expanded in June 2024 to include adults 50-59 years of age at increased risk for RSV-associated lower respiratory tract disease. In this paper, we describe the protocol of a postmarketing safety study evaluating the association between adjuvanted RSVPreF3 and new-onset Guillain-Barré syndrome (GBS), acute disseminated encephalomyelitis (ADEM) and atrial fibrillation (AF) among adults ≥50 years of age in the USA and provide our rationale for key methodological decisions. METHODS AND ANALYSIS: The potential associations between adjuvanted RSVPreF3 and GBS, ADEM and AF will be evaluated using secondary healthcare data and the self-controlled risk interval (SCRI) design. Data from five research partners in the USA spanning August 2023 through June 2030 will be used for the conduct of yearly monitoring queries and, sample size permitting, SCRI analyses. Claims-based definitions for new-onset outcomes (first diagnosis in 365 days) are: ≥1 inpatient diagnosis for GBS and ADEM; ≥1 inpatient or ≥2 ambulatory/emergency diagnoses for AF. The primary risk and control windows are 1-42 and 43-84 days, respectively, for GBS and ADEM; and 1-8 and 9-16 days for AF. SCRI analyses for GBS and ADEM will include chart-confirmed cases. SCRI analyses for AF will adjust for the positive predictive value obtained from validation against charts. Conditional Poisson regression will be used to calculate incidence rate ratios. ETHICS AND DISSEMINATION: This study was approved by the Institutional Review Boards (IRB) of Harvard Pilgrim Health Care Institute; WIRB-Copernicus Group, Inc and its affiliates (collectively, 'WCG'); WCG IRB, Inc; and Sterling IRB, with Federal Wide Assurance (FWA) numbers FWA00000100, FWA00033319 and FWA00025632, respectively, for all participating research partners. Study results will be shared with the US FDA and publicly disseminated through national or international clinical or scientific conferences and peer-reviewed publications. REGISTRATION: This protocol has been registered in the Heads of Medicines Agencies-European Medicines Agency Real World Data Catalogues (EUPAS1000000486).
Serial vaccination expands and refines human CD4 <sup>+</sup> T cell memory
bioRxiv (Cold Spring Harbor Laboratory) · 2026-04-13
articleOpen accessAbstract CD4 + T cells coordinate protective immunity against pathogens. However, a major unresolved question is how human CD4 + T cell memory is established and evolves following primary and repeated vaccination. Using COVID-19 mRNA vaccination as a model, we tracked 50 distinct antigen-specific populations directly ex vivo with peptide–MHC class II tetramers in eight SARS-CoV-2–naïve individuals from pre-vaccine baseline through memory time points after three mRNA doses. Our findings identify the primary vaccine series as the main driver of memory pool size. It leverages pre-existing memory while preferentially recruiting high-avidity T cells, establishing an immunodominance hierarchy dominated by a small subset of precursors. Booster vaccination refines both the magnitude and quality of T cell memory. It increases select populations and enhances differentiation of subdominant CD4 + T cells. Populations that did not become more abundant after boosting retained their polyfunctional potential. Beyond establishing memory to the ancestral spike, vaccinations broadened responses by recruiting cross-reactive T cells recognizing viral variants. Collectively, these findings reveal how human CD4 + T cell memory evolves through sequential immunizations to generate a functionally diverse and broadly responsive memory repertoire against future viral challenges.
Research in Autism · 2026-01-12
articleOpen accessPain · 2025-12-24
articleABSTRACT: The validity of enriched enrollment randomized withdrawal (EERW) trials to evaluate the efficacy of opioids for the treatment of chronic pain has been questioned. Enriched enrollment randomized withdrawal trials include an open-label titration phase to identify treatment responders who tolerate the drug, followed by a double-blind randomized phase in which responders either continue the drug or switch to placebo. A key concern is that the apparent efficacy of opioids in EERW trials may be attributable to induction of withdrawal symptoms among participants switched to placebo. We used individual participant data from 13 EERW trials (N = 5070) submitted to the US Food and Drug Administration (FDA) to estimate the extent to which withdrawal symptoms mediated the treatment effect of opioids on pain. The primary mediator was the maximum Subjective Opioid Withdrawal Scale score during the randomized phase. The primary outcome was the change in pain intensity (numeric rating scale) from randomization baseline to week 12. The pooled average treatment effect was -0.71 (95% confidence interval [CI], -0.87 to -0.55) on the numeric rating scale. Withdrawal symptoms did not significantly mediate the effect of opioids on pain overall, accounting for 2% of the pooled treatment effect (95% CI, -1% to 4%). However, significant mediation was observed in 3 individual trials (range, 8% to 28% of treatment effect mediated). Although withdrawal symptoms did not systematically bias efficacy findings in EERW trials of opioids submitted to the FDA, they contributed to overestimation in some cases. These findings support incorporating mediation analyses in future EERW trials to ensure accurate interpretation of study results.
Open Forum Infectious Diseases · 2025-01-29
articleOpen accessAbstract Background Extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) are a major global threat, and there is a significant gap in research on the burden and associated risk factors for ESCrE in low-and middle income countries(LMICs). This is particularly true for people with HIV (PWH), who make up a significant proportion of the population in sub-Saharan Africa. In Botswana, 20% of individuals aged 15-49 are PWH. The risk factors associated with ESCrE colonization, typically a precursor to infection, are important to understand as such infections can result in increased healthcare costs as well as high morbidity and mortality. Methods Within a larger regional surveillance study, 546 adults with HIV were recruited from clinics and communities in 3 districts and underwent interviews and rectal sampling. ESCrE was defined as Enterobacterales demonstrating non-susceptibility to ceftriaxone or ceftazidime. Results 27% of participants screened positive for ESCrE colonization. The mean CD4 count was 635 cells/mm3 (SD± 267). Table 1 describes the demographics of the participants with and without ESCrE colonization. Escherichia coli was the most commonly isolated ESCrE (146/174; 84%). Bivariate and multivariate analysis was used to determine risk factors associated with ESCrE colonization (Table 2). Recent hospitalization and certain geographic locations were independent risk factors for ESCrE colonization. Recent antibiotic use had an elevated OR for ESCrE colonization that did not achieve statistical significance in adjusted analysis. Conclusion These results add to the limited data on risk factors associated with ESCrE colonization in PWH. Hospitalization is an independent risk factor for colonization despite controlling for antibiotic use, which suggests the need for further investigation into hospital-specific factors that contribute to ESCrE colonization. Further research is needed to understand the geographic differences in ESCrE colonization in this setting. As LMICs with high HIV burdens build capacity for antimicrobial stewardship and infection prevention infrastructure in healthcare, research on unique potential mechanisms that result in multi-drug resistant colonization in PWH may impact strategies and priorities to combat antimicrobial resistance. Disclosures Robert Gross, MD, MSCE, Pfizer Inc: DSMB member for drug unrelated to study
PAIN Reports · 2025-06-05
articleOpen accessIntroduction: No prediction models exist for the success for buprenorphine initiation in opioid-naïve patients or in transition from other opioids in patients treated for chronic pain. Objectives: To create a prediction model for the successful use of buprenorphine to treat chronic pain. Methods: Stepwise Akaike information criterion prediction modeling procedures were applied to a harmonized participant-level data set of 10 enriched enrollment randomized withdrawal clinical trials of buprenorphine submitted to the Food and Drug Administration. Available baseline factors and nine patient-reported outcomes were considered to predict success with the titration (10 studies) and maintenance of benefit after randomization (5 studies). Patient-reported outcomes were modeled separately given inconsistent use across studies. Results: No prediction model reached an area under the receiver operator curve ≥0.70, the threshold for clinical usefulness. Successful initiation or transition of buprenorphine was accomplished in 3541 of 6052 (58.7%) participants, and 614 of 877 (70.0%) completed the 12-week maintenance phase with no difference between opioid-experienced and opioid-naïve participants. Only a medical history of obesity and baseline pain were retained in the overall titration model and only baseline pain in the maintenance model. Only brief pain inventory and subject opioid withdrawal scores were retained in the titration subsets containing those measures. Conclusion: No clinically useful prediction models of clinical benefit were identified, but a few covariates may be of interest in future studies of the initiation of buprenorphine in opioid-naïve patients or of transition from other opioids to buprenorphine. The lack of a predictor supports considering a trial of buprenorphine in clinically relevant scenarios for patients without known opioid use disorder, including careful monitoring and an a priori plan to deal with any problems that may occur.
Recent grants
NIH · $17.0M · 2018
Mental Health Biostatistics Training Grant
NIH · $1.3M · 2003–2020
Frequent coauthors
- 230 shared
Ebbing Lautenbach
- 218 shared
Sean Hennessy
University of Pennsylvania
- 124 shared
Brian L. Strom
Rutgers, The State University of New Jersey
- 106 shared
Ruben C. Gur
Children's Hospital of Philadelphia
- 103 shared
Charles E. Leonard
University of Pennsylvania
- 101 shared
Colleen M. Brensinger
University of Pennsylvania
- 86 shared
Pam Tolomeo
University of Pennsylvania
- 80 shared
Irving Nachamkin
University of Pennsylvania
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