Reviewing the Reproduction Number R in Covid-19 Models

Most of the epidemiological models of the Covid-19 pandemic contain the reproduction number (R) as a parameter. In this article we focus on some shortcomings regarding its role in driving health policies and political decisions. First, we summarize what R is and what it is used for. Second, we introduce a three-question matrix for the evaluation of any construct or parameter within a model. We then review the main literature about R to highlight some of its shortcomings and apply to them our three-question matrix. Finally, we argue that these shortcomings are important for an epistemic and political evaluation of R.