Comparing the responses of the UK, Sweden and Denmark to COVID-19 using counterfactual modelling

Swapnil Mishra,Samir Bhatt,Charles Whittaker,H Juliette T Unwin,Christl A Donnelly,Harrison H Zhu,Axel Gandy,Anne Cori,Michaela Vollmer,Melodie Monod,Lilith K Whittles,Daniel J Laydon,Oliver Ratmann,Neil M Ferguson,Helen Coupland,Thomas A Mellan,James A Scott,Seth Flaxman,Katy A M Gaythorpe

doi:10.1038/s41598-021-95699-9

Swapnil Mishra, Samir Bhatt + Show 17 more

Open Access

https://doi.org/10.1038/s41598-021-95699-9

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Journal: Scientific Reports	Publication Date: Aug 11, 2021
Citations: 29	License type: open-access

Affiliation: Imperial College London, University of Oxford

Abstract

The UK and Sweden have among the worst per-capita COVID-19 mortality in Europe. Sweden stands out for its greater reliance on voluntary, rather than mandatory, control measures. We explore how the timing and effectiveness of control measures in the UK, Sweden and Denmark shaped COVID-19 mortality in each country, using a counterfactual assessment: what would the impact have been, had each country adopted the others’ policies? Using a Bayesian semi-mechanistic model without prior assumptions on the mechanism or effectiveness of interventions, we estimate the time-varying reproduction number for the UK, Sweden and Denmark from daily mortality data. We use two approaches to evaluate counterfactuals which transpose the transmission profile from one country onto another, in each country’s first wave from 13th March (when stringent interventions began) until 1st July 2020. UK mortality would have approximately doubled had Swedish policy been adopted, while Swedish mortality would have more than halved had Sweden adopted UK or Danish strategies. Danish policies were most effective, although differences between the UK and Denmark were significant for one counterfactual approach only. Our analysis shows that small changes in the timing or effectiveness of interventions have disproportionately large effects on total mortality within a rapidly growing epidemic.

Highlights

The United Kingdom (UK) and Sweden have among the worst per-capita COVID-19 mortality in Europe
We address the counterfactual question: how would the Swedish approach to COVID-19 management have affected the epidemics of Denmark and the UK? what impact would the policies of those two countries have had on the Swedish epidemic? Our aim is to inform future decision-making by illuminating how the timing and effectiveness of interventions interacted to influence the final disease burden experienced by a country
Sweden and the UK all managed to suppress the first wave of their respective epidemics

Summary

Introduction

The UK and Sweden have among the worst per-capita COVID-19 mortality in Europe. Sweden stands out for its greater reliance on voluntary, rather than mandatory, control measures. We explore how the timing and effectiveness of control measures in the UK, Sweden and Denmark shaped COVID19 mortality in each country, using a counterfactual assessment: what would the impact have been, had each country adopted the others’ policies? Behavioural data (Fig. 1b,c) suggest that the major difference between Sweden, the UK, and Denmark was the rapidity with which population contact rates were reduced, rather than the extent of this reduction. Denmark and Sweden are neighbours with demographic, social and economic similarities, and both countries experienced similar initial profiles of per-capita COVID-19 mortality (Fig. 1a). We include the UK in our analysis because it is another Northern European country that experienced similar cumulative per-capita COVID-19 mortality to Sweden, while adopting control policies similar to those of Denmark

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