COVID 19: Pandemic assessment and management using Incidence(calc)(t+14) and herd immunity - Habere nos alia modum?

The course of the COVID-19 pandemic is commonly evaluated using the 7-day Incidence. We propose using 1) Incidence(calc)(t+14), an index for the theoretical course of the pandemic in the absence of lockdown, as a basis for making real-time interventions. 2) The derived parameters t(alpha)(t) and t(alpha_stable)(S), obtained with the SIZ algorithm and the Bateman function, for estimating of the required degree of herd immunity to stop the pandemic. The current value of t(alpha)(t) for Germany is similar to 1.8 days, indicating that the percentage herd immunity required to halt the pandemic, assuming an efficacy of vaccination of 90%, is at least 87%.