Reduction of COVID-19 incidence across Europe in the early spring months of 2021 led to substantial relaxation of restrictions in summer, despite the emergence and spread of the more transmissible SARS-CoV-2 delta variant. As expected, this relaxation led to a renewed increase in incidence. How should Europe act, what strategies should it adopt, and what specific risks should it consider moving forward? 1 These questions become even more pressing, since emerging data indicates the delta variant is more infectious and partially evades immune response. Europe needs a coherent and effective strategy before schools fully reopen and the transmission of SARS-CoV-2 further increases due to seasonality in autumn. Two opposing strategies are considered: either continue to rapidly lift restrictions, assuming the combination of past natural exposure and current vaccination coverage would allow a high incidence …