Background: Restrictions on mobility have been implemented by many countries to limit the spread of novel coronavirus infection (COVID-19) yet have important social and economic consequences. Their impact on reducing transmission is, however, inadequately understood.
Methods: We examined the association of COVID-19 incidence rates with mobility changes, defined as changes in categories of domestic location, against a pre-pandemic baseline, using country-specific daily incidence data on newly confirmed COVID-19 cases and mobility data collected from mobile devices in all 34 OECD countries plus Singapore and Taiwan. The study period was from the day of the 100th case in each country to August 31, 2020. Daily incidence rates were lagged by 14 days and regressed to mobility changes using LOESS regression and logit regression.
Findings: In two thirds of examined countries, reductions of up to 40% in commuting mobility (to workplaces, transit stations, retailers, and recreation) were associated with decreased COVID-19 incidence, more so early in the pandemic. However, these decreases plateaued as mobility remained low or decreased further. We found smaller or negligible associations between mobility restriction and incidence rates in the late phase in most countries.
Interpretation: Mild to moderate degrees of mobility restriction in most countries were associated with reduced incidence rates of COVID-19 that appear to attenuate over time, while some countries exhibited no effect of such restrictions. More detailed research is needed to precisely understand the benefits and limitations of mobility restrictions as part of the public health response to the COVID-19 pandemic.
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