Fig. 1.

Schematization of the four types of admissible optimal control and legend of the plot colors that will be used throughout the paper. White (panel a) denotes a constant control at its maximum value. Different shades of gray denote delayed controls applied at the switching time ${\tau }_s^{*}$. We distinguish three different behaviors, depending on the position of ${\tau }_s^{*}$ with respect to the infectious dynamics: the switch occurs before the peak of the infection (panel b, light gray), in correspondence of the peak (panel c, gray) or after the peak of infection (panel d, dark gray).