Combining models to generate a consensus effective reproduction number <![CDATA[ $R$ ]]> for the COVID-19 epidemic status in England
Manley H., Park J., Bevan L., Sanchez-Marroquin A., Danelian G., Bayley T., Bowman V., Maishman T., Finnie T., Charlett A., Watkins NA., Hutchinson J., Riley S., Panovska-Griffiths J.
The effective reproduction number was widely accepted as a key indicator during the early stages of the COVID-19 pandemic. In the UK, the value published on the UK Government Dashboard has been generated as a combined value from an ensemble of epidemiological models via a collaborative initiative between academia and government. In this paper we outline this collaborative modelling approach and illustrate how, by using an established combination method, a combined estimate can be generated from an ensemble of epidemiological models. We analyse the values calculated for the period between April 2021 and December 2021, to show that this is robust to different model weighting methods and ensemble size, and that using heterogeneous data sources for validation increases its robustness and reduces the biases and limitations associated with a single source of data. We discuss how can be generated from different data sources and is therefore a good summary indicator of the current dynamics in an epidemic.