A Simple Method of Measuring Vaccine Effects on Infectiousness and Contagion

作     者：Yasutaka Chiba 

作者机构：Division of Biostatistics Clinical Research Center Kinki University School of Medicine Osaka Japan 

出 版 物：《Open Journal of Statistics》 (统计学期刊（英文）)

年 卷 期：2013年第3卷第4期

页      面：7-15页

学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学] 

主　　题：Indirect Effect Interference Mediation Analysis Potential Outcome Principal Stratification 

摘      要：The vaccination of one person may prevent another from becoming infected, either because the vaccine may prevent the first person from acquiring the infection and thereby reduce the probability of transmission to the second, or because, if the first person is infected, the vaccine may impair the ability of the infectious agent to initiate new infections. The former mechanism is referred as a contagion effect and the latter is referred as an infectiousness effect. By applying a principal stratification approach, the conditional infectiousness effect has been defined, but the contagion effect is not defined using this approach. Recently, new definitions of unconditional infectiousness and contagion effects were provided by applying a mediation analysis approach. In addition, a simple relationship between conditional and unconditional infectiousness effects was found under a number of assumptions. These two infectiousness effects can be assessed by very simple estimation and sensitivity analysis methods under the assumptions. Nevertheless, such simple methods to assess the contagion effect have not been discussed. In this paper, we review the methods of assessing infectiousness effects, and apply them to the inference of the contagion effect. The methods provided here are illustrated with hypothetical vaccine trial data.