This paper provides estimates of COVID-19 effective reproduction numbers worldwide and explains their evolution for selected European countries since the start of the pandemic taking account of changes in voluntary and government mandated social distancing, incentives to comply, vaccination and the emergence of mutations. Evidence based on panel data modeling indicates that the diversity of outcomes that we document resulted from the non-linear interaction of mandated and voluntary social

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... cing and the economic incentives that governments provided to support isolation, with no one factor independently capable of lowering the reproduction number below one. However, the importance of these factors declined over time, with vaccine uptake driving heterogeneity in country experiences in 2021. Our approach also allows us to identify the basic reproduction number, R 0 , and how it changes with mutations. It is precisely estimated and differs little across countries.