  The determination of the infection fatality rate (IFR) for the novel
SARS-CoV-2 coronavirus is a key aim for many of the field studies that are
currently being undertaken in response to the pandemic. The IFR together with
the basic reproduction number $R_0$, are the main epidemic parameters
describing severity and transmissibility of the virus, respectively. The IFR
can be also used as a basis for estimating and monitoring the number of
infected individuals in a population, which may be subsequently used to inform
policy decisions relating to public health interventions and lockdown
strategies. The interpretation of IFR measurements requires the calculation of
confidence intervals. We present a number of statistical methods that are
relevant in this context and develop an inverse problem formulation to
determine correction factors to mitigate time-dependent effects that can lead
to biased IFR estimates. We also review a number of methods to combine IFR
estimates from multiple independent studies, provide example calculations
throughout this note and conclude with a summary and "best practice"
recommendations. The developed code is available online.
