Fig. 4.

The top three panels show logistic fits to COVID variant transitions. If the fraction of cases due to the new variant, x(t), was the solution of a logistic equation, then $\log (x(t)/(1-x(t))$ would be linear. In the bottom panel, we plot this transformation of the three curves. The resulting plots are approximately linear with R² values 0.98, 0.97, and 0.98, respectively.