R0 unfortunately turns out to be a basically meaningless number for COVID. In theory it is a natural property of the virus. Other measures of R like Rt are then

R0 unfortunately turns out to be a basically meaningless number for COVID. In theory it is a natural property of the virus. Other measures of R like Rt are then the 'adjusted' rates that take into account environmental factors. In reality none of these numbers have any scientific validity, as they are usually computed using methodologies that aren't valid. In particular R0 is often simply a free variable in a model, i.e. a fudge factor in which the values are brute forced until the model output comes into line with reported government statistics. What does this fudge factor represent, if anything? Nobody actually knows, so it gets labelled R and then announced as a "fact" by epidemiologists. But then someone else takes a slightly different data set and runs the same calculation, but with a totally different R0 value coming out the other end.