Before revision: Short answer: not much, and only with lots of caution. The paper presents a suitable mathematical model of the process for feedback control analysisand uses well-known results from control theory to prove that suppression strategies can be effective if enacted very early , while mitigation strategies , including trying to achieve herd immunity, are likely to fail .
After revision: This paper studies if and to which extent COVID-19 epidemics can be controlled by authorities taking decisions on public health measures on the basis of daily reports of swab test results, active cases and total cases. A suitably simplified process model is derived to support the controllability analysis, highlighting the presence of very significant time delay; the model is validated with data from several outbreaks. The analysis shows that suppression strategies can be effective if enacted very early , while mitigation strategies , including trying to achieve herd immunity, are likely to fail .