Effectiveness of Granular Lockdown as an Epidemic Control Strategy in Kerala, India

Background Lockdown is a time-tested methodology to cease infectious disease spread. The national and subnational lockdown effectively reduced the spread of COVID-19 in many countries, including India. The current article documents the effectiveness of lockdown at a more granular level, that is, the local self-government (LSG), the lowest administrative unit, in Kerala, a south Indian state. Methods We extracted all data pertaining to this study: the distribution of containment zones and the incidence of COVID-19 cases from official data sources of the Government of Kerala. As part of the study, we followed the progression of all LSGs as containment zones over the study period of 10 weeks (7/5/2020-15/7/2020). We created survival distributions characterizing the time to enter lockdown and the time to remain in lockdown for all the districts and the state. Finally, we conducted an interdistrict comparison of the cumulative incidence of COVID-19 per population for 6 months after the period of LSG containment was over to ascertain its effectiveness. Results Four northern districts of Kerala state had implemented lockdown strategy more rigorously both in the proportion of LSGs that has become a containment zone and in the period of containment compared to the rest of Kerala. As a result, the growth of COVID-19 cases in these 4 districts was less (7.5 times) than in the other districts (37 times) during the study period. However, the reduction in the disease incidence was not instantaneous; at the same time, it was not short-living as the difference continued to exist for 6 more months past lockdown. Conclusion Implementing granular lockdown strategies can effectively control the spread of disease only if it encompasses a sufficient area for an adequate period. We believe our research could help governments provide insights into the years-long and never-ending battle with the pandemic.