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

  1. Moaath K. Mustafa Ali
  2. Yazan Samhouri
  3. Marwa Sabha
  4. Lynna Alnimer

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Abstract

Background

There 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.

Methods

We 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.

Results

The 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.

Conclusion

The 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.

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  1. ScreenIT

    SciScore for 10.1101/2020.08.13.20174706: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Innate to non-randomized designs, our study has some limitations. England and Sweden are geographically separated, hence other confounders or co-interventions may have affected the outcomes. Time-varying confounders, including seasonality, can threaten the internal validity of ITS analysis. Authors believe this is unlikely due to several reasons. Both countries used similar tools to measure outcomes [19, 21]. Second, England and Sweden have a comparable life expectancy (80.8 vs. 81.1 years, respectively) suggestive of similar health quality [40]. Lastly, the COVID-19 pandemic started at the same time in both counties. This study only addresses short-term outcomes of lockdown order; the authors analyzed data of the first 100 days post-lockdown. Long-term trends in COVID-19 infection were not addressed and may increase after phase 3 of lockdown loosening in England. In conclusion, the lockdown implemented in England did result in a statistically and epidemiologically significant reduction in the COVID-19 daily new cases rate compared to Sweden. The decline in daily cases also resulted in a drop in daily death rate related to COVID-19 in England. Lockdown in England has successfully halted COVID-19 transmission in the short-term. However, long term outcomes are unknown, and a new epidemic during winter is possible. Future research is needed to understand the long-term net outcome of the anti-COVID-19 policy implemented in both countries.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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  2. Version published to 10.1101/2020.08.13.20174706v1 on medRxiv