Report 26: Reduction in mobility and COVID-19 transmission
Pierre Nouvellet, Sangeeta Bhatia, Anne Cori, Kylie E. C. Ainslie, Marc Baguelin, Bhatt, Samir, Adhiratha Boonyasiri, Nicholas F. Brazeau, Lorenzo Cattarino, Laura Cooper, Helen Coupland, Zulma M. Cucunubá, Gina Cuomo-Dannenburg, Amy Dighe, A Djaafara, Ilaria Dorigatti, Oliver Eales, Sabine van Elsland, Nscimento, Fabricia, Richard G. FitzJohn, Katy A. M. Gaythorpe, Lily Geidelberg, Nicholas C. Grassly, W Green, Arran Hamlet, Katharina Hauck, Wes Hinsley, Natsuko Imai, Benjamin Jeffrey, Edward Knock, Daniel J. Laydon, John A. Lees, Tara D. Mangal, Thomas A. Mellan, G Nedjati Gilani, Kris V. Parag, M Pons Salort, Manon Ragonnet‐Cronin, Riley, Steven, H. Juliette T. Unwin, Robert Verity, Michaela Vollmer, Erik Volz, Phoebe Walker, Caroline E. Walters, H Wang, Oliver J. Watson, Charles Whittaker, Lilith K. Whittles, Xin Xi, Neil M. Ferguson, Christl A. Donnelly
Abstract
In response to the COVID-19 pandemic, countries have sought to control transmission of SARS-CoV-2 by restricting population movement through social distancing interventions, reducing the number of contacts. Mobility data represent an important proxy measure of social distancing. Here, we develop a framework to infer the relationship between mobility and the key measure of population-level disease transmission, the reproduction number (R). The framework is applied to 53 countries with sustained SARS-CoV-2 transmission based on two distinct country-specific automated measures of human mobility, Apple and Google mobility data. For both datasets, the relationship between mobility and transmission was consistent within and across countries and explained more than 85% of the variance in the observed variation in transmissibility. We quantified country-specific mobility thresholds defined as the reduction in mobility necessary to expect a decline in new infections (R<1). While social contacts were sufficiently reduced in France, Spain and the United Kingdom to control COVID-19 as of the 10th of May, we find that enhanced control measures are still warranted for the majority of countries. We found encouraging early evidence of some decoupling of transmission and mobility in 10 countries, a key indicator of successful easing of social-distancing restrictions. Easing social-distancing restrictions should be considered very carefully, as small increases in contact rates are likely to risk resurgence even where COVID-19 is apparently under control. Overall, strong population-wide social-distancing measures are effective to control COVID-19; however gradual easing of restrictions must be accompanied by alternative interventions, such as efficient contacttracing, to ensure control.