Cluster‐randomized trials are often conducted to assess vaccine effects. Defining estimands of interest before conducting a trial is integral to the alignment between a study's objectives and the data to be collected and analyzed. This paper considers estimands and estimators for overall, indirect, and total vaccine effects in trials, where clusters of individuals are randomized to vaccine or control. The scenario is considered where individuals self‐select whether to participate in the trial, and the outcome of interest is measured on all individuals in each cluster. Unlike the overall, indirect, and total effects, the direct effect of vaccination is shown in general not to be estimable without further assumptions, such as no unmeasured confounding. An illustrative example motivated by a cluster‐randomized typhoid vaccine trial is provided.

中文翻译：

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整群随机疫苗试验中的估计和推断。

通常进行整群随机试验以评估疫苗效果。在进行试验之前定义感兴趣的估计值是使研究目标与要收集和分析的数据保持一致不可或缺的一部分。本文考虑了试验中总体、间接和总疫苗效应的估计量和估计量，其中将一组个体随机分配到疫苗组或对照组。考虑个体自行选择是否参与试验的场景，并且对每个集群中的所有个体测量感兴趣的结果。与整体效应、间接效应和总体效应不同，疫苗接种的直接效应通常在没有进一步假设的情况下无法估计，例如没有不可测量的混杂因素。提供了一个由整群随机伤寒疫苗试验激发的说明性例子。