Gonçalves Bronner P, Olliaro Piero L, Horby Peter, Cowling Benjamin J
From the ISARIC, Pandemic Sciences Institute, University of Oxford, Oxford, United Kingdom.
Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.
Epidemiology. 2025 Sep 1;36(5):646-649. doi: 10.1097/EDE.0000000000001877. Epub 2025 Jun 17.
Here, we posit that studies comparing outcomes of patients hospitalized with COVID-19 by vaccination status are important descriptive epidemiologic studies, but they contrast two groups that are not comparable with regard to causal analyses. We use the principal stratification framework to show that these studies can estimate a causal vaccine effect only for the subgroup of individuals who would be hospitalized with or without vaccination. Further, we describe the methodology for, and present sensitivity analyses of, this effect. Using this approach can change the interpretation of studies only reporting the standard analyses that condition on observed hospital admission status-that is, analyses comparing outcomes for all hospitalized COVID-19 patients by vaccination status.
在此，我们认为，按疫苗接种状况比较COVID-19住院患者结局的研究是重要的描述性流行病学研究，但在因果分析方面，它们所对比的两组并不具有可比性。我们使用主分层框架来表明，这些研究仅能估计出对于无论接种与否都会住院的个体亚组的因果疫苗效应。此外，我们描述了这种效应的方法并进行了敏感性分析。采用这种方法可能会改变仅报告基于观察到的住院状态进行标准分析的研究的解释，即按疫苗接种状况比较所有COVID-19住院患者结局的分析。
