A follow-on from comment #14, Laherrere calculated a Hubbert Linearization on COVID-19 numbers from several countries here:


As with using the technique for oil, a set of numbers from the curve can linearize but if another growth acceleration occurs after it settles down, its clear that it's not predicting an ultimate herd immunity level. It's just temporarily keeping it at bay.

And if the curve follows the "Abroad" trajectory as shown below, then the HL will flatline to an infinite x-interception since the inflection point has yet to be reached and there's no sign of bending in the cumulative (on a semi-log plot).