Between Geography and Demography: Key Interdependencies and Exit Mechanisms for Covid-19

Antonio Scala; Andrea Flori; Alessandro Spelta; Emanuele Brugnoli; Matteo Cinelli; Walter Quattrociocchi; Fabio Pammolli

is the (which was not peer-reviewed) The copyright holder for this preprint . Finally, we notice that to each lockdown strength α corresponds an effective reproductive number R eff 0 = αR 0 ; hence, for α ∼ α crit = 1/R 0 , the epidemics is expected to stay in a quiescent state where it does not either grow or decay sensibly. On the other hand, for α < α crit the epidemics decreases; nevertheless, since this happens before a sufficient number of recovered individuals has built up herd-immunization, the height of the peaks after the lockdown lifting are almost unchanged if compared with the no lockdown scenario. Again, a "too good" intervention risks to postpone the problem without attenuating it. Notice that, if one applies lockdowns with α < α crit , it could be necessary to switch back and forth to lockdown to avoid the peak go beyond the capacity of a national healthcare system (see Fig. 9 ).