Early Social Distancing Policies in Europe, Mobility Change and COVID‐19 Case Trajectories: Lessons from Spring 2020

Abstract

Research Objective Nonpharmacological policies aimed at improving physical distancing, such as shelter in place orders or gathering bans are a central strategy used to mitigate disease spread, particularly in the early life‐course of a pandemic. We sought to assess the relationship between different types of early social distancing policies implemented across Europe, how they related to changes in population mobility and subsequent COVID‐19 case growth. Study Design Data on national social distancing policies were obtained from the Oxford COVID‐19 Government Response Tracker (OxCGRT). For each European country we defined index dates based on the implementation of the country's first social distancing policy. We then compared the value of each mobility metric in the week after the index date versus the 7‐day period extending from 9 to 2 days prior to the index date. We included a two‐day washout period given the volatility that typically precedes these orders. For mobility, each country was compared to itself over time. We employed a pre‐post comparison and two linear mixed‐effects models to first assess the relationship between policies and observed changes in mobility, and to assess the relationship between changes in mobility and rates of COVID‐19 infections in subsequent weeks. Aggregated and anonymized mobility data was obtained from Google. This data is similar to publicly accessible “Community Mobility Reports,” with the addition of novel variables, such as relative change in the average number of hours individuals spent away from their primary place of residence. Population Studied Our analytic sample included 6075 country‐day observations across 27 European countries. Principal Findings Spain saw the largest mobility decrease from the pre‐COVID baseline, as measured by the time spent away from residence, with a decline in aggregate mobility of nearly 70%. Sweden had the smallest decrease with approximately a 20% decline from baseline at the end of the study period (April 12th 2020). Policies associated with the largest decline in mobility were: mandatory stay‐at‐home orders, followed by mandatory workplace closures, school closures and non‐mandatory workplace closures. While mandatory shelter‐in‐place orders were associated with 16.7% less mobility (95% CI: −23.7% to −9.7%), non‐mandatory orders were only associated with an 8.4% decrease (95% CI: −14.9% to −1.8%). Large‐gathering bans saw the least change in mobility compared with other policy types. We, in turn, found a strong link between changes in mobility and changes in COVID‐19 case growth. Overall, a 10% decrease in the average time spent away from places of residence was associated with 11.8% (95% CI: 3.8%, 19.1%) fewer new cases two weeks later. A more pronounced 50% decrease resulted in 46.6% fewer cases two weeks later (95% CI: 17.5%, 65.4%). Conclusions Social distancing policies had a significant but heterogeneous impact on mobility. Across countries studied, relative change in time spent away from home was positively associated with slowed c...