A Simple Method of Measuring Vaccine Effects on Infectiousness and ContagionReport as inadecuate

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The vaccination of one person may prevent another from becominginfected, either because the vaccine may prevent the first person fromacquiring the infection and thereby reduce the probability of transmission tothe second, or because, if the first person is infected, the vaccine may impairthe ability of the infectious agent to initiate new infections. The formermechanism is referred as a contagion effect and the latter is referred as aninfectiousness effect. By applying a principal stratification approach, theconditional infectiousness effect has been defined, but the contagion effect isnot defined using this approach. Recently, new definitions of unconditionalinfectiousness and contagion effects were provided by applying a mediationanalysis approach. In addition, a simple relationship between conditional andunconditional infectiousness effects was found under a number of assumptions.These two infectiousness effects can be assessed by very simple estimation andsensitivity analysis methods under the assumptions. Nevertheless, such simplemethods to assess the contagion effect have not been discussed. In this paper,we review the methods of assessing infectiousness effects, and apply them tothe inference of the contagion effect. The methods provided here areillustrated with hypothetical vaccine trial data.


Indirect Effect; Interference; Mediation Analysis; Potential Outcome; Principal Stratification

Cite this paper

Y. Chiba -A Simple Method of Measuring Vaccine Effects on Infectiousness and Contagion,- Open Journal of Statistics, Vol. 3 No. 4A, 2013, pp. 7-15. doi: 10.4236-ojs.2013.34A002.

Author: Yasutaka Chiba

Source: http://www.scirp.org/


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