Evaluation of the UK's COVID-19 public health policy "Shielding: Results of a linked data matched cohort study

Objective:
To assess outcomes associated with shielding, introduced during the COVID-19 pandemic across the UK to protect those at highest risk of harm.

Study design:
Linked data and questionnaires in matched cohorts from the population of Wales, UK.

Methods:
We compared individual-level linked routine and self-reported outcomes between people identified for shielding (n = 123,293) and comparators (n = 120,997) matched by age, sex, and previous health service utilisation. We sent questionnaires to 1500 randomly sampled people in each cohort.

Results:
At one year 6·1 % of shielded people had contracted SARS-CoV-2 compared to 6·2 % in the matched cohort (Adjusted Odds Ratio [AOR] 0·970; 95 % confidence interval [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 %; AOR 2·280; 95 % CI 2·190 to 2·374; and 1·1 % vs 0·8 %; AOR 1·430; 95 % CI 1·308 to 1·563, respectively).

About 1/3 completed questionnaires (n = 1015), with linkage possible in 752 cases (shielded: n = 411; matched: n = 341). Shielded respondents reported lower physical and mental health (SF12 PCS difference: −3·752; 95 % CI -4·823 to −2·682; 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.

Conclusion:
We found no evidence of a protective effect of shielding on SARS-CoV-2 infections or COVID-19 related mortality, an increased rate of hospital acquired infections and increased self-isolation. Shielding during a future pandemic should only be considered alongside effective measures to reduce healthcare associated infections.