Timing of national lockdown and mortality in COVID-19: The Italian experience

Objective: To evaluate if the pandemic mitigation effects of lockdown in Italy have been influenced by the level of penetration of COVID-19 in Italian Regions at the onset of containment (March 9, 2020).

Methods: We collected data published day by daily from the first COVID-19 case until May 3, 2020, the end of lockdown, by Italy's Protezione Civile Department. Linear regression analyses were performed to evaluate possible correlations between the number of confirmed cases/100.000 residents and the number of new cases/100.000/day before lockdown, with the number of deaths/100.000 residents at sixty days, in each Italian region.

Results: We found a significant positive correlation between the number of confirmed cases before lockdown and mortality up to sixty days (p < 0.001; R² = 0.57) as well as between the incidence rate of new cases per day and mortality up to sixty days (p < 0.001; R² = 0.73). Regression coefficients indicated about two deaths up to sixty days for every new patient with confirmed COVID-19 before lockdown, and 37 deaths for every new infected subject per day until the lockdown decree of March 9, 2020.

Conclusions: Every new infected subject before lockdown counted on the death toll of the COVID-19 pandemic in Italy.