Inferring a cause-effect relationship between lockdown restrictions and COVID-19 pandemic trend during the first wave

•COVID-19 pandemic induced most of the world governments to implement lockdown measures.•We developed an epidemic model for the most affected countries in Europe.•Our model resulted to be matching appropriately with daily and cumulative counts.•We inferred a possible cause-effect relationship between the lockdown and new cases.•Lockdowns created economics damage, but unthinkable results were obtained in brief time.