Evaluating the Impacts of Tiered Restrictions Introduced in England, During October and December 2020 on COVID-19 Cases: A Synthetic Control Study

Background: In 2020, a second wave of COVID-19 cases unevenly affected places in England leading to the introduction of a tiered system with different restrictions implemented geographically. Whilst previous research has examined the impact of national lockdowns on transmission, there has been limited research examining the marginal effect of differences in localised restrictions or how these effects vary by deprivation. Methods: We examined how Tier 3 restrictions affected COVID-19 case rates, and how these effects varied by level of deprivation, using data on weekly reported cases for 7201 neighbourhoods in England and adjusting these for changing case-detection rates. We identified areas that entered Tier 3 restrictions in October and December, constructed a synthetic control group of places under Tier 2 restrictions, and compared changes in weekly infections over a 4-week period. We used interaction analysis to estimate whether this effect varied by level of deprivation and the prevalence of a new variant (B.1.1.7). Results: The introduction of Tier 3 restrictions in October and December was associated with a 14% (95% CI 10% to 19%) and 20% (95% CI 13% to 29%) reduction in infections respectively, compared to the rates expected with Tier 2 restrictions only. The effects were similar across levels of deprivation and by the prevalence of the new variant. Interpretation: Compared to Tier 2 restrictions, additional restrictions on hospitality and meeting outdoors introduced in Tier 3 areas in England had a moderate effect on transmission and these restrictions did not appear to increase inequalities in COVID-19 cases.Funding Statement: BB, XZ are supported by the National Institute for Health Research(NIHR) Gastrointestinal Health Protection Research Unit. BB is also supported by the NIHR Applied Research Collaboration North West Coast (ARC NWC). GO is supported by the NIHR School for Public Health Research. IB is supported by NIHR Senior Investigator award. The viewsexpressed in this publication are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social.Declaration of Interests: None to declare