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No Evidence That Shielding the Vulnerable Reduced COVID Infections

The previously untested pandemic policy of 'shielding' vulnerable people to reduce their risk of infection during the pandemic had no clear impact on infection rates. That conclusion, drawn from a new study by researchers from Swansea University, was based on data from Wales, but "as shielding policy was similar across the UK", the findings were "of relevance in other countries too", they said.  

The shielding policy was introduced in March 2020 in an attempt to protect those thought to be at highest risk of serious harm should they catch COVID-19. Those targeted had existing conditions such as cancer, severe respiratory disorders, or diseases requiring immunosuppressive treatment. They were sent personal communications by letter, text, or email strongly advising them to stay at home and to self-isolate for at least 12 weeks, including from anyone – even family members – sharing the same premises.

Policy Introduced 'Without Evidence'

In the new study, published in Public Health, researchers said the policy was introduced "without prior evidence of effects on health outcomes, costs or behaviour". So they conducted a linked data retrospective study using electronic health records routinely collected for the entire Welsh population, and compared the 117,415 people told to shield with the rest of the population (3,086,385) who were not.

The largest clinical categories in the shielded cohort were: severe respiratory conditions (35.5%), immunosuppressive therapy (25.9%) and cancer (18.6%). People in the shielded cohort were more likely to be female, aged 50 years and older, living in relatively deprived areas, care home residents, and frail. The authors noted that although people living in care homes were intended to be excluded from shielding, they found more than 1000 care home residents in the shielded cohort, almost double the proportion of care home residents in the general population.

As expected given that the shielded cohort were sicker than the general population, they had higher overall rates of death and of healthcare utilisation. However when the team examined COVID-19 infections, deaths, and admissions to hospital and intensive care, the infection rate was only marginally higher in the shielded cohort (5.9%) than in the general population (5.7%), even though the proportion of shielded people tested for COVID-19 was higher (odds ratio 1.616; 95% CI 1.597 to 1.637).

Study Raises Questions About the Benefit of Shielding

The authors said: "Lack of clear impact on infection rates raises questions about the success of shielding." 

Helen Snooks, professor of health services research at Swansea University Medical School, who led the research, said: "Our study found no evidence of reduced COVID-19 infections one year after shielding was introduced. This raises questions about the benefits of shielding for vulnerable people as a policy."  

The authors noted: "Shielding was an untested public health policy that was introduced in the United Kingdom early in the pandemic," and "was based on assumptions rather than evidence of effectiveness".  

Professor Snooks added: "Work is ongoing to compare these outcomes, as well as self-reported quality of life, with a matched group of people who were clinically vulnerable, but not selected for shielding. 

"Having as much evidence as possible about the effect of policies is essential if we are to learn lessons for the future."

The project, known as EVITE Immunity, was funded through the National Core Studies Immunity Programme and commissioned by Birmingham University on behalf of UKRI. It involves collaborations with Cardiff University, Warwick University, Welsh Government, and NHS Wales. The authors declared that they have no competing interests.