Estimating the COVID-19 R number: a bargain with the devil?

Abstract

The basic reproduction number R0 is the average number of infections produced by a single infectious person in a population with no immunity. R0 has a close relative named the effective reproduction number R: the average number of infections produced by a single infected person in a population with partial immunity. In The Lancet Infectious Diseases2, Li and colleagues estimate how the imposition and lifting of non-pharmaceutical interventions (NPIs) changed the R number for SARS-CoV-2 in 131 countries in the first half of 2020.