Government Restriction Efficiency on Curbing COVID-19 Pandemic Transmission in Western Europe

The World Health Organization (WHO)-confirmed pandemic (March 2020) of the new Coronavirus 2 severe acute respiratory syndrome infection (SARS-CoV-2) reported in Wuhan, China, in December 2019 (first reported cases), then spread to Italy and successively around the world. The objective of this study is to evaluate the effectiveness of the restrictions implemented by different governments from a statistical point of view. We quantitatively evaluated how restrictions influenced the temporal evolution of the distribution of the weekly number of hospitalized patients in the intensive care unit (ICU) for different countries that applied different levels of restrictions, which can be summarized with the average stringency index, a synthetic index that represents a metric for quantifying the severity of the restrictions applied. We found that the stringency index is strongly correlated with the distribution skewness, while standard deviation and kurtosis are poorly and moderately influenced. Furthermore, we compared the values of the skewness of the distribution of hospitalized patients during several pre-pandemic influenza outbreaks in Italy (data not available for other countries). Analysis shows that for normal flu, there is a substantial difference in skewness (as much as 70%) in the distribution with respect to the first COVID-19 pandemic outbreak, where social restrictions were applied. This large difference highlights that the restrictions implemented modify the symmetry of the peak of the distribution of the hospitalized patient in the ICU. Therefore, skewness can be used as a valid indicator to assess whether restriction has any effect on pandemic transmission and can be used as a support for decision makers.