Featured Publications
Public Health Impacts of Vaccines for COVID-19 and Beyond: Opportunities to Overcome Technical and Regulatory Barriers for Randomized Trials.
Kennedy-Shaffer L. Public Health Impacts of Vaccines for COVID-19 and Beyond: Opportunities to Overcome Technical and Regulatory Barriers for Randomized Trials. American Journal Of Public Health 2023, 113: 778-785. PMID: 37104734, PMCID: PMC10262256, DOI: 10.2105/ajph.2023.307302.Peer-Reviewed Original ResearchConceptsPublic health impactCOVID-19 pandemicPopulation healthEvidence baseCOVID-19Health impactsInfectious disease outbreaksCommunity levelRandomized trialsIndividual levelRegulatory barriersPivotal trialsClinical benefitTrialsClinical trialsVaccine trialsPrevent infectionStrategic deploymentVaccineHealthThe required size of cluster randomized trials of nonpharmaceutical interventions in epidemic settings
Sheen J, Haushofer J, Metcalf C, Kennedy‐Shaffer L. The required size of cluster randomized trials of nonpharmaceutical interventions in epidemic settings. Statistics In Medicine 2022, 41: 2466-2482. PMID: 35257398, PMCID: PMC9111156, DOI: 10.1002/sim.9365.Peer-Reviewed Original ResearchConceptsCluster randomized trialEffectiveness of interventionsSample sizeRandomized trialsPlanning such trialsApproximate sample size formulaeReduce transmissionEffect sizeNonpharmaceutical interventionsInfectious disease outbreaksObservational studyInterventionEpidemic settingsSample size methodsAdequate powerSARS-CoV-2 pandemicSARS-CoV-2 transmissionSample size formulaTested individualsSimulated bankTreatment effectsTrialsCommunity transmissionOutbreak settingsSize formulaStatistical Properties of Stepped Wedge Cluster-Randomized Trials in Infectious Disease Outbreaks
Kennedy-Shaffer L, Lipsitch M. Statistical Properties of Stepped Wedge Cluster-Randomized Trials in Infectious Disease Outbreaks. American Journal Of Epidemiology 2020, 189: 1324-1332. PMID: 32648891, PMCID: PMC7604531, DOI: 10.1093/aje/kwaa141.Peer-Reviewed Original ResearchConceptsWedge trialsParallel-arm cluster-randomized trialsStepped wedge cluster randomized trialStatistical propertiesCluster randomized trialStatistical disadvantageStepped wedge trialIndividual randomizationInfectious disease outbreaksCluster randomized designEvaluation of interventionsEvaluate various designsTrial designDetect intervention effectsWedge designRandomized controlled trialsIntervention effectsEffect estimatesControlled trialsParallel-armEpidemic settingsLogistical factorsAdequate powerInfectious disease incidenceRandomized trialsSample size estimation for stratified individual and cluster randomized trials with binary outcomes
Kennedy‐Shaffer L, Hughes M. Sample size estimation for stratified individual and cluster randomized trials with binary outcomes. Statistics In Medicine 2020, 39: 1489-1513. PMID: 32003492, PMCID: PMC7247053, DOI: 10.1002/sim.8492.Peer-Reviewed Original ResearchConceptsCluster randomized trialIndividual randomized trialsIntracluster correlation coefficientSample size estimationBinary outcomesRandomized trialsSample sizeStratify individualsLogistic regressionSample size reductionProbabilities of eventsContinuous outcomesSize estimationStratified trialCorrelation coefficientOutcomesTrialsEstimationProbabilityNovel methods for the analysis of stepped wedge cluster randomized trials
Kennedy‐Shaffer L, de Gruttola V, Lipsitch M. Novel methods for the analysis of stepped wedge cluster randomized trials. Statistics In Medicine 2019, 39: 815-844. PMID: 31876979, PMCID: PMC7247054, DOI: 10.1002/sim.8451.Peer-Reviewed Original ResearchConceptsSW-CRTsRobust inference proceduresStepped wedge cluster randomized trialParametric model assumptionsModel assumptionsCluster randomized trialNonparametric analysis methodsTheoretical propertiesInference proceduresNonparametric methodsIncorporating covariatesRestrictive assumptionsAssumptionsEffects modelControl approachFeasibility advantagesSynthetic control approachIncreased powerRandomized trialsIntervention clustersMixed effects modelsEstimationTime trendsInterventionModel-based approach
2021
Power and sample size calculations for cluster randomized trials with binary outcomes when intracluster correlation coefficients vary by treatment arm
Kennedy-Shaffer L, Hughes M. Power and sample size calculations for cluster randomized trials with binary outcomes when intracluster correlation coefficients vary by treatment arm. Clinical Trials 2021, 19: 42-51. PMID: 34879711, PMCID: PMC8883478, DOI: 10.1177/17407745211059845.Peer-Reviewed Original ResearchConceptsWorking correlation structureIntracluster correlation coefficientIntracluster correlation coefficient valuesAsymptotic varianceCorrelation structureClustered binary dataSample size requirementsSample size calculationCluster-level covariatesExchangeable working correlation structureCluster randomized trialModest-sized clustersBinary covariateSize calculationBinary outcomesBinary dataDistribution of cluster sizesFormulaCluster size distributionSize requirementsCovariatesEquationsSample sizeCluster sizeRandomized trials