Automated local lockdowns for SARS-CoV-2 epidemic control – assessment of effect by controlled interrupted time series analysis

Abstract

BackgroundDuring COVID-19, broad NPIs like national lockdowns were effective but had significant drawbacks, prompting targeted approaches like Denmark's localized lockdowns based on specific epidemiological criteria. This study evaluates the impact of Denmark's strategy on epidemic control to inform future response. MethodsRegister-based controlled interrupted time series analysis, examining SARS-CoV-2 infection rates in Danish parishes from March to September, 2021. Matching of control parishes was based on location, time, and pre-lockdown infection trends, with the lockdown's start defined as the day after a parish exceeded the lockdown criteria. Follow up included three-weeks pre-lockdown and two-weeks post-lockdown. ResultsThirty parishes were mandated to lockdown, approximately 3.5% of the population of Denmark. A total of 94 control parishes were used as 109 controls. The decrease in the incidence during the 2-week follow-up period after initiation of the lockdown was 13% points higher in case parishes: In case parishes, incidence was reduced by 78% compared to 65% in control parishes. ConclusionsOur findings demonstrate that local lockdowns did have a positive effect in mitigating the spread of the SARS-CoV-2 virus, making them valuable in the fight against the COVID-19-pandemic and an important alternative to national lockdowns.