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Background: Initiation of proprotein convertase subtilisin/kexin type 9 monoclonal antibody (PCSK9 mAb) for lipid-lowering following myocardial infarction (MI) is likely affected by patients' prognostic factors, potentially leading to bias when comparing real-world treatment effects., Methods: Using target-trial emulation, we assessed potential confounding when comparing two treatment strategies post-MI: initiation of PCSK9 mAb within 1 year and no initiation of PCSK9 mAb. We identified MI hospitalizations during July 2015-June 2020 for patients aged ≥18 years in Optum's de-identified Clinformatics Data Mart (CDM) and MarketScan, and those aged ≥66 in the US Medicare claims database. We estimated a 3-year counterfactual cumulative risk and risk difference (RD) for 10 negative control outcomes using the clone-censor-weight approach to address time-varying confounding and immortal person-time., Results: PCSK9 mAb initiation within 1-year post-MI was low (0.7% in MarketScan and 0.4% in both CDM and Medicare databases). In CDM, there was a lower risk for cancer (RD = -3.6% [95% CI: -4.3%, -2.9%]), decubitus ulcer (RD = -7.7% [95% CI: -11.8%, -3.7%]), fracture (RD = -8.1% [95% CI: -9.6%, -6.6%]), influenza vaccine (RD = -9.3% [95% CI: -17.5%, -1.1%]), and visual test (RD = -0.6% [95% CI: -0.7%, -0.6%]) under the PCSK9 mAb initiation versus no initiation strategy. Similar differences persisted in the MarketScan and Medicare databases. In each database, ezetimibe and low-density lipoprotein testing were unbalanced between treatment strategies., Conclusion: A comparative effectiveness study of these treatments using the current approach would likely bias results due to the low number of PCSK9 mAb initiators., Competing Interests: R.S. was an employee of Amgen at the time of completion of the study. A.B. was an employee of Target RWE at the time of the study completion. L.D.C. receives research support from Amgen. A.G.A. and Y.Y. are employees of Target RWE. S.S. and N.D. are employees of Amgen. P.M. received research support and consulting fees from Amgen. M.A.B. has served on scientific advisory committees for Amgen, AbbVie, Atara Biosciences, Brigham and Women’s Hospital, NIDDK, and Vertex; and he is a consulting chief scientist and owns equity in Target RWE. No other author reports no conflicts of interest., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Remdesivir is recommended for certain hospitalized patients with COVID-19. However, these recommendations are based on evidence from small randomized trials, early observational studies, or expert opinion. Further investigation is needed to better inform treatment guidelines with regard to the effectiveness of remdesivir among these patients., Methods: We emulated a randomized target trial using chargemaster data from 333 US hospitals from 1 May 2020 to 31 December 2021. We compared three treatment protocols: remdesivir within 2 days of hospital admission, no remdesivir within the first 2 days of admission, and no remdesivir ever. We used baseline comorbidities recorded from encounters up to 12 months before admission and identified the use of in-hospital medications, procedures, and oxygen supplementation from charges. We estimated the cumulative incidence of mortality or mechanical ventilation/extracorporeal membrane oxygenation with an inverse probability of censoring weighted estimator. We conducted analyses in the total population as well as in subgroups stratified by level of oxygen supplementation., Results: A total of 274,319 adult patients met the eligibility criteria for the study. Thirty-day in-hospital mortality risk differences for patients adhering to the early remdesivir protocol were -3.1% (95% confidence interval = -3.5%, -2.7%) compared to no early remdesivir and -3.7% (95% confidence interval -4.2%, -3.2%) compared to never remdesivir, with the strongest effect in patients needing high-flow oxygen. For mechanical ventilation/extracorporeal membrane oxygenation, risk differences were minimal., Conclusions: We estimate that, among hospitalized patients with COVID-19, remdesivir treatment within 2 days of admission reduced 30-day in-hospital mortality, particularly for patients receiving supplemental oxygen on the day of admission., Competing Interests: A.B. is an employee of and owns equity in Regeneron Pharmaceuticals. At the time of writing, he was an employee of NoviSci/Target RWE. C.W. is an employee of and owns equity in NoviSci/Target RWE. A.A. has received consulting fees from Merck and Gilead; her institution has received funding from Merck and Gilead for her research. R.S.B. receives research and consulting grants from Gilead, as well as institutional grants from TARGET-HCC, TARGET-NASH, and HCV-TARGET. C.L. receives research funding from Gilead, Pfizer, and Lilly. K.R.R. serves as an advisor to Spark Therapeutics, Mallinckrodt, Novo Nordisk, and Genfit; he receives research support (paid to the University of Pennsylvania) from Gilead, Merck, BMS, Intercept, Exact Sciences, Biovie, Sequana, Grifols, TARGET-HCC, HCV-TARGET, and TARGET-NASH; he serves on a DSMB for Novartis. E.C.V. declares no conflicts of interest. J.M.C. is an employee of and owns equity in Target RWE. A.M. is an employee of and owns equity in Target RWE. M.W.F. is Chief Medical Officer for TARGET RWE and receives personal fees and is a stockholder in the company. M.A.B. serves on scientific advisory committees for AbbVie, Amgen, Astellas/Seagan, Atara Biotherapeutics, Brigham and Women’s Hospital, Kite/Gilead, and Vertex; he receives consulting fees and owns equity in NoviSci/Target RWE., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Prior studies suggest neighborhood poverty and deprivation are associated with adverse health outcomes including death, but evidence is limited among persons with HIV, particularly women. We estimated changes in mortality risk from improvement in three measures of area-level socioeconomic context among participants of the Women's Interagency HIV Study., Methods: Starting in October 2013, we linked geocoded residential census block groups to the 2015 Area Deprivation Index (ADI) and two 2012-2016 American Community Survey poverty variables, categorized into national tertiles. We used parametric g-computation to estimate, through March 2018, impacts on mortality of improving each income or poverty measure by one and two tertiles maximum versus no improvement., Results: Of 1596 women with HIV (median age 49), 91 (5.7%) were lost to follow-up and 83 (5.2%) died. Most women (62%) lived in a block group in the tertile with the highest proportions of individuals with income:poverty <1; 13% lived in areas in the tertile with the lowest proportions. Mortality risk differences comparing a one-tertile improvement (for those in the two highest poverty tertiles) in income:poverty <1 versus no improvement increased over time; the risk difference was -2.2% (95% confidence interval [CI] = -3.7, -0.64) at 4 years. Estimates from family income below poverty level (-1.0%; 95% CI = -2.7, 0.62) and ADI (-1.5%; 95% CI = -2.8, -0.21) exposures were similar., Conclusions: Consistent results from three distinct measures of area-level socioeconomic environment support the hypothesis that interventions to ameliorate neighborhood poverty or deprivation reduce mortality risk for US women with HIV. See video abstract at, http://links.lww.com/EDE/B863., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Important questions exist regarding the comparative effectiveness of alternative childhood vaccine schedules; however, optimal approaches to studying this complex issue are unclear., Methods: We applied methods for studying dynamic treatment regimens to estimate the comparative effectiveness of different rotavirus vaccine (RV) schedules for preventing acute gastroenteritis-related emergency department (ED) visits or hospitalization. We studied the effectiveness of six separate protocols: one- and two-dose monovalent rotavirus vaccine (RV1); one-, two-, and three-dose pentavalent rotavirus vaccine (RV5); and no RV vaccine. We used data on all infants to estimate the counterfactual cumulative risk for each protocol. Infants were censored when vaccine receipt deviated from the protocol. Inverse probability of censoring-weighted estimation addressed potentially informative censoring by protocol deviations. A nonparametric group-based bootstrap procedure provided statistical inference., Results: The method yielded similar 2-year effectiveness estimates for the full-series protocols; weighted risk difference estimates comparing unvaccinated children to those adherent to either full-series (two-dose RV1, three-dose RV5) corresponded to four fewer hospitalizations and 12 fewer ED visits over the 2-year period per 1,000 children. We observed dose-response relationships, such that additional doses further reduced risk of acute gastroenteritis. Under a theoretical intervention to fully vaccinate all children, the 2-year risk differences comparing full to observed adherence were 0.04% (95% CI = 0.03%, 0.05%) for hospitalizations and 0.17% (95% CI = 0.14%, 0.19%) for ED visits., Conclusions: The proposed approach can generate important evidence about the consequences of delaying or skipping vaccine doses, and the impact of interventions to improve vaccine schedule adherence., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Modern causal inference methods allow machine learning to be used to weaken parametric modeling assumptions. However, the use of machine learning may result in complications for inference. Doubly robust cross-fit estimators have been proposed to yield better statistical properties., Methods: We conducted a simulation study to assess the performance of several different estimators for the average causal effect. The data generating mechanisms for the simulated treatment and outcome included log-transforms, polynomial terms, and discontinuities. We compared singly robust estimators (g-computation, inverse probability weighting) and doubly robust estimators (augmented inverse probability weighting, targeted maximum likelihood estimation). We estimated nuisance functions with parametric models and ensemble machine learning separately. We further assessed doubly robust cross-fit estimators., Results: With correctly specified parametric models, all of the estimators were unbiased and confidence intervals achieved nominal coverage. When used with machine learning, the doubly robust cross-fit estimators substantially outperformed all of the other estimators in terms of bias, variance, and confidence interval coverage., Conclusions: Due to the difficulty of properly specifying parametric models in high-dimensional data, doubly robust estimators with ensemble learning and cross-fitting may be the preferred approach for estimation of the average causal effect in most epidemiologic studies. However, these approaches may require larger sample sizes to avoid finite-sample issues., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Since being introduced to epidemiology in 2000, marginal structural models have become a commonly used method for causal inference in a wide range of epidemiologic settings. In this brief report, we aim to explore three subtleties of marginal structural models. First, we distinguish marginal structural models from the inverse probability weighting estimator, and we emphasize that marginal structural models are not only for longitudinal exposures. Second, we explore the meaning of the word "marginal" in "marginal structural model." Finally, we show that the specification of a marginal structural model can have important implications for the interpretation of its parameters. Each of these concepts have important implications for the use and understanding of marginal structural models, and thus providing detailed explanations of them may lead to better practices for the field of epidemiology.