Impact of Covid-19 Response Strategies on the Rate of Change in Mortality in Europe During the First and Second Waves: A Retrospective Cohort Study

The coronavirus disease 2019 (COVID-19) has led to more than 3,000,000 deaths globally. During the first year of the pandemic, countries have focused their response strategies on non-pharmaceutical interventions (NPIs) such as lockdowns and use of facial coverings. Because of collateral effects (psycho-social, and economical) by NPIs, investigating their effectiveness is increasingly important for optimal policies. The aim of this study is to investigate whether varying degrees of response strategies affect the rate of change in mortality at specific time points in the epidemic. The containment and health index (CHI) is used to identify the degree of response measures adopted by each country. Six time points around the peak of daily mortality are identified for the first two epidemiological waves for 40 European countries. The response was then correlated to the rate of change of mortality observed over one week 26 days later (time lag for the intervention to take effect). Spearman’s rank correlation coefficient was used for the unadjusted analysis, and multiple linear regression is used in the adjusted analysis. The intensity of CHI reduced the rate of increase of mortality before the first epidemic peak but had no detectable effect at any other time point. Different covariates and interactions between CHI and covariates such as population density and GDP, affected the rate of change of mortality at different time points during the two waves. NPIs may be effective, as suggested by a significant effect of CHI on mortality early in the first wave. However, the effect is not consistent across time points, and the extent of collateral damage suggests a closer look at other factors influencing the epidemic is necessary