What Were the Effects of the UK's COVID-19 Public Health Policy 'Shielding'? Results of Linked Data Matched Cohort Study

Background: Shielding was introduced during the COVID-19 pandemic across the UK to protect those at highest risk of serious harm. We assessed effects of shielding on health outcomes and behaviours. Methods: Within Wales we compared individual-level linked routinely collected and self-reported outcomes between people identified for shielding and comparators matched by age, sex, and pre-pandemic health service utilisation. Findings: We matched people identified for shielding (n = 123,293) in Wales to comparators (n = 120,997). Cohorts were well matched for age, sex and ethnicity; those from the shielded cohort were more likely to be frailer and living in areas of higher deprivation. At 1 year 6·1% of people in the shielded cohort contracted SARS-CoV-2 compared to 6·2% in the matched cohort (Adjusted Odds Ratio (OR) 0·970; 95% CI 0·937 to 1·004. Suspected healthcare associated infections were more likely in shielded people (1·1% vs 0·6%; AOR 1·678; 95% CI 1·529 to 1·842). All cause and COVID-19 related deaths were higher in the shielded cohort (7·0% vs 3·5%; OR 2·280; 95% CI 2·190 to 2·374; and 1·1% vs 0·8%; OR 1·430; 95% CI 1·308 to 1·563, respectively). Approximately 1/3 of randomly sampled people completed questionnaires (n = 1015/3000), with linkage possible in n = 752 cases (shielded: n = 411; matched: n = 341). Respondents in the shielded cohort reported lower physical health (SF12 PCS difference: -3·752; 95% CI -4·823 to -2·682) and slightly lower mental health (SF12 MCS difference: -1·217; 95% CI -2·580 to 0·145). They were more likely to have strictly avoided contact; stayed at home; felt scared to go outside; and were less likely to have gone out for shopping, leisure or travel. Interpretation: Shielding did not protect people from SARS-CoV-2 infection or COVID-19 related mortality. This evidence does not support implementation of shielding in a future pandemic. Funding: This study was funded through the National Core Studies Immunity programme (led from Birmingham University), in turn funded by the Medical Research Council [MR/V028367/1]; Health Data Research UK [HDR-9006], which receives its funding from the UK Medical Research Council, Engineering and Physical Sciences Research Council, Economic and Social Research Council, Department of Health and Social Care (England), Chief Scientist Office of the Scottish Government Health and Social Care Directorates, Health and Social Care Research and Development Division (Welsh Government), Public Health Agency (Northern Ireland), British Heart Foundation (BHF) and the Wellcome Trust; and Administrative Data Research UK, which is funded by the Economic and Social Research Council [grant ES/S007393/1]. This work was also supported by the Wales COVID-19 Evidence Centre, funded by Health and Care Research Wales Declaration of Interest: HS and AE are expert witnesses to the UK COVID Inquiry. HS is an editor of the NIHR Journals Library. AW is a member of the NIHR HS&DR funding committee. HS, MK and AP have received grants from UKRI-MRC, NIHR and HCRW; RL and RP from UKRI-MRC, UKRI-ESCR and HDRUK; AE from HCRW; AW from UKR-MRC, NIHR and HCRW; JD from NIHR; JL from ADR Wales. SJ has received support from CSL Behring, Pharming, Octapharma, UCB Pharma, LFB, Biocryst, Kedrion, Biotest, SOBI, Grifols, Takeda, Sanofi, GSK, The Binding Site, Stratech and HCRW. The other authors declare no interests. Ethical Approval: The EVITE Immunity study has received approval from the Newcastle North Tyneside 2 Research Ethics Committee (IRAS 295050).