Background: In March 2020, India imposed a strict nationwide lockdown, making social distancing the primary nonpharmacologic mitigation strategy for the COVID-19 pandemic. To date, there has not been a comprehensive evaluation of the policy’s impact on mobility changes and state-level trajectory of COVID case growth. Understanding the effectiveness of the initial lockdown will inform policy efforts, given rising case counts in India following relaxation of the lockdown.

Methods: Using a dataset on aggregated mobility changes in India, we conducted a retrospective interrupted time series analysis between February 15th and April 26th, 2020 to assess the combined impact of India’s nationwide curfew and lockdown on aggregate community mobility. Our primary outcomes were change in mobility to retail and recreation sites and change in state-level COVID-19 case growth rate. Secondary outcomes included mobility changes to other sites and time spent at home. We next assessed state-level variation. Finally, we examined the relationship between changes in aggregate mobility and the case growth rate of COVID-19.

Findings: We observed an immediate and pronounced decrease in mobility following the policy’s implementation for all location categories examined. For our primary outcome, the national lockdown was associated with an 86% decrease to retail and recreational sites. However, the effects were not homogeneously sustained in the post-policy period. Visits to grocery stores and pharmacies (slope= 0.62% increase in visits per day) and transit stations (slope= 0.24%) began to recover, whereas visits to retail and recreation (slope=-0.41%), and parks (slope-0.47%) continued to decline during the post period. Significant state-level variation in mobility response was observed (71% to 95% decrease in visits to retail and recreation sites). States with the largest decrease in visits to retail and recreational sites were associated with a 7.2% rate of increase of COVID-19 in contrast to those states with the lowest decrease in mobility, which exhibited a 53% rate increase in COVID-19 cases (p= 0.03).

Interpretation: Our findings provide early evidence that India’s nationwide policy has been effective in both achieving its initial goal of decreased mobility and slowing the spread of COVID-19 cases. As the policy was nationwide, further research is needed to understand the drivers of state-level variation in mobility and COVID-19 case growth.