Social Distancing with Movement Restrictions and the Effective Replication Number of COVID-19: Multi-Country Analysis Based on Phone Mobility Data

Linking phone mobility data to the effective replication number (Rt) could help evaluation of the impact of social distancing on the coronavirus disease 2019 (COVID-19) spread and estimate the time lag (TL) needed for the effect of movement restrictions to appear. We used a time-series analysis to discover how patterns of five indicators of mobility data relate to changes in Rt of 125 countries distributed over three groups based on Rt-mobility correlation. Group 1 included 71 countries in which Rt correlates negatively with residential and positively with other mobility indicators. Group 2 included 25 countries showing an opposite correlation pattern to Group 1. Group 3 included the 29 remaining countries. We chose the best-fit TL based on forecast and linear regression models. We used linear mixed models to evaluate how mobility indicators and the stringency index (SI) relate with Rt. SI reflects the strictness of governmental responses to COVID-19. With a median of 14 days, TLs varied across countries as well as across groups of countries. There was a strong negative correlation between SI and Rt in most countries belonging to Group 1 as opposed to Group 2. SI (units of 10%) associated with decreasing Rt in Group 1 [{beta} -0.15, 95% CI -0.15 - (-0.14)] and Group 3 [-0.05, -0.07 - (-0.03)], whereas, in Group 2, SI associated with increasing Rt (0.13, 0.11 - 0.16). Mobile phone mobility data could contribute evaluations of the impact of social distancing with movement restrictions on the spread of the COVID-19.