Background: When a randomized controlled trial fails to demonstrate statistically significant efficacy against the primary endpoint, a potentially costly new trial would need to be conducted to receive licensure. Incorporating data from previous trials might allow for more efficient follow-up trials to demonstrate efficacy, speeding the availability of effective vaccines. Methods: Based on the outcomes from a failed trial of a maternal vaccine against respiratory syncytial virus (RSV), we simulated data for a new Bayesian group-sequential trial. We analyzed the data either ignoring data from t ..read more

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The interpretation of vaccine efficacy estimands is subtle, even in randomized trials designed to quantify the immunologic effects of vaccination. In this article, we introduce terminology to distinguish between different vaccine efficacy estimands and clarify their interpretations. This allows us to explicitly consider the immunologic and behavioral effects of vaccination, and establish that policy-relevant estimands can differ substantially from those commonly reported in vaccine trials. We further show that a conventional vaccine trial allows the identification and estimation of different v ..read more

Background: Drug overdose persists as a leading cause of death in the United States, but resources to address it remain limited. As a result, health authorities must consider where to allocate scarce resources within their jurisdictions. Machine learning offers a strategy to identify areas with increased future overdose risk to proactively allocate overdose prevention resources. This modeling study is embedded in a randomized trial to measure the effect of proactive resource allocation on statewide overdose rates in Rhode Island (RI). Methods: We used statewide data from RI from 2016 to 2020 t ..read more

Approaches to address measurement error frequently rely on validation data to estimate measurement error parameters (e.g., sensitivity and specificity). Acquisition of validation data can be costly, thus secondary use of existing data for validation is attractive. To use these external validation data, however, we may need to address systematic differences between these data and the main study sample. Here, we derive estimators of the risk and the risk difference that leverage external validation data to account for outcome misclassification. If misclassification is differential with respect t ..read more

Background: Observational studies are used for estimating vaccine effectiveness under real-world conditions. The practical performance of two common approaches—cohort and test-negative designs—need to be compared for COVID-19 vaccines. Methods: We compared the cohort and test-negative designs to estimate the effectiveness of the BNT162b2 vaccine against COVID-19 outcomes using nationwide data from the United States Department of Veterans Affairs. Specifically, we (1) explicitly emulated a target trial using follow-up data and evaluated the potential for confounding using negative controls and ..read more

Background: We illustrate a method for stratum assignment in small cohort studies that avoids modeling assumptions. Methods: Off-the-shelf software (rgenoud) made stratum assignments to minimize a loss function built on within-stratum and population-adjusted Euclidean distances. Results: In 100 trials using simulated data of 300 records with a binary treatment and four dissimilar covariate treatment predictors, minimizing a loss based on Euclidean distance reduced covariate imbalance by a median of 99%. Stratification by propensity score and weighting records by the inverse of their probabilit ..read more

Background: In the United States, over 80% of tuberculosis (TB) disease cases are estimated to result from reactivation of latent TB infection (LTBI) acquired more than 2 years previously (“reactivation TB”). We estimated reactivation TB rates for the US population with LTBI, overall, by age, sex, race–ethnicity, and US-born status, and for selected comorbidities (diabetes, end-stage renal disease, and HIV). Methods: We collated nationally representative data for 2011–2012. Reactivation TB incidence was based on TB cases reported to the National TB Surveillance System that were attributed to L ..read more

Background: Studies have suggested Medicaid expansion enacted in 2014 has resulted in a reduction in overall cardiovascular disease (CVD) mortality in the United States. However, it is unknown whether Medicaid expansion has a similar effect across race–ethnicity and sex. We investigated the effect of Medicaid expansion on CVD mortality across race–ethnicity and sex. Methods: Data come from the behavioral risk factor surveillance system and the US Centers for Disease Control’s Wide-ranging Online Data for Epidemiologic Research, spanning the period 2000–2019. We used the generalized synthetic c ..read more

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