The objective of our observational study is to evaluate the association between public health non-pharmaceutical interventions (exposure) against the COVID-19 outbreak and the incidence of confirmed COVID-19 cases(outcome) from five countries : France, Italy, Japan, South Korea, and the USA, December 31, 2019 through April 12, 2020. The incidence of COVID-19 would be significantly greater without lockdown (1.89 times, p-value <.0001), public health and economic measures (25.17, p-value <.0001), and using masks (11.93, p-value=0.002), assuming that all other public health policies are the same
