tetano
Editor, Senior Moderator
CMAJ
. 2021 Apr 7;cmaj.210132.
doi: 10.1503/cmaj.210132. Online ahead of print.
The mobility gap: estimating mobility thresholds required to control SARS-CoV-2 in Canada
Kevin A Brown[SUP] 1 [/SUP], Jean-Paul R Soucy[SUP] 1 [/SUP], Sarah A Buchan[SUP] 1 [/SUP], Shelby L Sturrock[SUP] 1 [/SUP], Isha Berry[SUP] 1 [/SUP], Nathan M Stall[SUP] 1 [/SUP], Peter J?ni[SUP] 1 [/SUP], Amir Ghasemi[SUP] 1 [/SUP], Nicholas Gibb[SUP] 1 [/SUP], Derek R MacFadden[SUP] 1 [/SUP], Nick Daneman[SUP] 1 [/SUP]
Affiliations
Abstract
Background: Nonpharmaceutical interventions remain the primary means of controlling severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) until vaccination coverage is sufficient to achieve herd immunity. We used anonymized smartphone mobility measures to quantify the mobility level needed to control SARS-CoV-2 (i.e., mobility threshold), and the difference relative to the observed mobility level (i.e., mobility gap).
Methods: We conducted a time-series study of the weekly incidence of SARSCoV-2 in Canada from Mar. 15, 2020, to Mar. 6, 2021. The outcome was weekly growth rate, defined as the ratio of cases in a given week versus the previous week. We evaluated the effects of average time spent outside the home in the previous 3 weeks using a log-normal regression model, accounting for province, week and mean temperature. We calculated the SARS-CoV-2 mobility threshold and gap.
Results: Across the 51-week study period, a total of 888 751 people were infected with SARS-CoV-2. Each 10% increase in the mobility gap was associated with a 25% increase in the SARS-COV-2 weekly case growth rate (ratio 1.25, 95% confidence interval 1.20-1.29). Compared to the prepandemic baseline mobility of 100%, the mobility threshold was highest in the summer (69%; interquartile range [IQR] 67%-70%), and dropped to 54% in winter 2021 (IQR 52%-55%); a mobility gap was present in Canada from July 2020 until the last week of December 2020.
Interpretation: Mobility strongly and consistently predicts weekly case growth, and low levels of mobility are needed to control SARS-CoV-2 through spring 2021. Mobility measures from anonymized smartphone data can be used to guide provincial and regional loosening and tightening of physical distancing measures.
. 2021 Apr 7;cmaj.210132.
doi: 10.1503/cmaj.210132. Online ahead of print.
The mobility gap: estimating mobility thresholds required to control SARS-CoV-2 in Canada
Kevin A Brown[SUP] 1 [/SUP], Jean-Paul R Soucy[SUP] 1 [/SUP], Sarah A Buchan[SUP] 1 [/SUP], Shelby L Sturrock[SUP] 1 [/SUP], Isha Berry[SUP] 1 [/SUP], Nathan M Stall[SUP] 1 [/SUP], Peter J?ni[SUP] 1 [/SUP], Amir Ghasemi[SUP] 1 [/SUP], Nicholas Gibb[SUP] 1 [/SUP], Derek R MacFadden[SUP] 1 [/SUP], Nick Daneman[SUP] 1 [/SUP]
Affiliations
- PMID: 33827852
- DOI: 10.1503/cmaj.210132
Abstract
Background: Nonpharmaceutical interventions remain the primary means of controlling severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) until vaccination coverage is sufficient to achieve herd immunity. We used anonymized smartphone mobility measures to quantify the mobility level needed to control SARS-CoV-2 (i.e., mobility threshold), and the difference relative to the observed mobility level (i.e., mobility gap).
Methods: We conducted a time-series study of the weekly incidence of SARSCoV-2 in Canada from Mar. 15, 2020, to Mar. 6, 2021. The outcome was weekly growth rate, defined as the ratio of cases in a given week versus the previous week. We evaluated the effects of average time spent outside the home in the previous 3 weeks using a log-normal regression model, accounting for province, week and mean temperature. We calculated the SARS-CoV-2 mobility threshold and gap.
Results: Across the 51-week study period, a total of 888 751 people were infected with SARS-CoV-2. Each 10% increase in the mobility gap was associated with a 25% increase in the SARS-COV-2 weekly case growth rate (ratio 1.25, 95% confidence interval 1.20-1.29). Compared to the prepandemic baseline mobility of 100%, the mobility threshold was highest in the summer (69%; interquartile range [IQR] 67%-70%), and dropped to 54% in winter 2021 (IQR 52%-55%); a mobility gap was present in Canada from July 2020 until the last week of December 2020.
Interpretation: Mobility strongly and consistently predicts weekly case growth, and low levels of mobility are needed to control SARS-CoV-2 through spring 2021. Mobility measures from anonymized smartphone data can be used to guide provincial and regional loosening and tightening of physical distancing measures.