England's Lockdown vs. Sweden's Herd Immunity: A Comparison of the Daily New COVID-19 Cases and Related Deaths Using Comparative Interrupted Time Series Analysis

BackgroundThere is a lack of empirical evidence that lockdowns decrease daily cases of COVID-19 and related mortality compared to herd immunity. England implemented a delayed lockdown on March 23, 2020, but Sweden did not. We aim to examine the effect of lockdown on daily COVID-19 cases and related deaths during the first 100 days post-lockdown. MethodsWe compared daily cases of COVID-19 infection and related mortality in England and Sweden before and after lockdown intervention using a comparative-interrupted time series analysis. The period included was from COVID-19 pandemic onset till June 30, 2020. ResultsThe adjusted-rate of daily COVID-19 infections was eight cases/10,000,000 person higher in England than Sweden before lockdown order (95% CI: 2-14, P=0.01). On the day of intervention (lagged lockdown), England had 693 more COVID-19 cases/10,000,000 person compared to Sweden (95% CI: 467-920, P<0.001). Compared to the pre-intervention period, the adjusted daily confirmed cases rate decreased by 19 cases/ 10,000,000 person compared to Sweden (95% CI: 13-26, P<0.001). There was a rate excess of 1.5 daily deaths/ 10,000,000 person in England compared to Sweden pre-intervention (95% CI: 1-2, P<0.001). The increased mortality rate resulted in 50 excess deaths/ 10,000,000 person related to COVID-19 in England compared to Sweden on the day of lockdown (95% CI: 30-71, P<0.001). Post-intervention, the rate of daily deaths in England decreased by two deaths/ 10,000,000 person compared to Sweden (95% CI: 1-3, P<0.001). During phases one and two of lockdown lifting in England, there was no rebound increase in daily cases or deaths compared to Sweden. ConclusionThe lockdown order implemented in England on March 23, 2020, effectively decreased the daily new cases rate and related mortality compared to Sweden. There was no short-term increase in COVID-19 cases and related-deaths after the phases one and two of the lifting of restrictions in England compared to Sweden. This study provides empirical, comparative evidence that lockdowns slow the spread of COVID-19 in communities compared to herd immunity.