对称疫苗效力 (Symmetric Vaccine Efficacy)

Traditional measures of vaccine efficacy (VE) are inherently asymmetric, constrained above by $1$ but unbounded below. As a result, VE estimates and corresponding confidence intervals can extend far below zero, making interpretation difficult and potentially obscuring whether the apparent effect reflects true harm or simply statistical uncertainty. The proposed symmetric vaccine efficacy (SVE) is a bounded and interpretable alternative to VE that maintains desirable statistical properties while resolving these asymmetries. SVE is defined as a symmetric transformation of infection risks, with possible values within $[-1, 1]$, providing a common scale for both beneficial and harmful vaccine effects. This paper describes the relationship between SVE and traditional VE, considers inference about SVE, and illustrates the utility of the proposed measure by reanalyzing data from a randomized trial of a candidate HIV vaccine. Open-source tools for computing estimates of SVE and corresponding confidence intervals are available in R through the sve package.

翻译：传统的疫苗效力（VE）度量本质上是非对称的，其上限受限于$1$，但下限无界。因此，VE估计值及相应的置信区间可能远低于零，导致解释困难，并可能掩盖表观效应反映的是真实危害还是单纯的统计不确定性。所提出的对称疫苗效力（SVE）是VE的一种有界且可解释的替代方案，它在保持理想统计特性的同时解决了这些不对称性问题。SVE定义为感染风险的对称变换，其可能取值在$[-1, 1]$范围内，为疫苗的有益和有害效应提供了一个统一的度量尺度。本文阐述了SVE与传统VE之间的关系，探讨了关于SVE的统计推断，并通过重新分析一项候选HIV疫苗随机试验的数据，说明了所提出度量的实用性。用于计算SVE估计值及相应置信区间的开源工具可通过R语言的sve包获取。