Quantifying the relationship between lockdowns, mobility, and effective reproduction number (Rt) during the COVID-19 pandemic in the Greater Toronto Area

Abstract Background The effectiveness of lockdowns in mitigating the spread COVID-19 has been subject intense debate. Data on relationship between public health restrictions, mobility, and pandemic growth so far conflicting. Objective We assessed restriction tiers, five contiguous units (PHUs) Greater Toronto Area (GTA) Ontario, Canada. Methods Weekly effective reproduction number (R t ) was calculated based daily cases each GTA March 1, 2020, 19, 2021. A global mobility index (GMI) for PHU using Google Mobility data. Segmented regressions were used to assess changes behaviour R over time. Pearson correlation coefficients GMI regression variable, accounting time lag 0, 7, 14 days. Results In all PHUs except Toronto, most rapid decline occurred first 2 weeks province-wide lockdown, this followed by a slight trend increased as restrictions decreased. This reversed September 6th October 10th after which decreased slightly without respect tier. began increase wave even before secular continued into summer, driven recreational spaces. reintroduced coincides with decreasing parks September. During wave, significant ( p < 0.01) days indicating moderate high viral rates, reflecting that incubation period brings time-lag effect human . second attenuated, only Durham at lockdown. Conclusions association stronger than wave. Public tiers did not alter existing toward