Shielding may have failed to protect people at most risk after a study showed that the clinically vulnerable were eight times more likely to test positive for Covid than the general population.
More than two million people were advised to shield by the Government, which meant staying at home and avoiding non-essential contact with household members.
It was hoped isolating the most at risk would save lives and prevent the NHS from being overwhelmed, and data from the Office for National Statistics (ONS) showed that about 95 per cent had complied.
However, Glasgow University found those shielding were far more likely to catch and die from Covid than the general population. Its study looked at more than 1.3 million people living in the Glasgow and Clyde area between March and May last year, of whom 27,747 were advised to shield.
The authors found that, compared to low-risk individuals, people advised to shield were eight times more likely to have confirmed Covid infections and five times more likely to die following confirmed infection.
Moderate risk individuals, such as people with diabetes, were four times more likely to have confirmed infections than the low risk group and five times more likely to die following confirmed infection.
While 0.13 per cent of the general population was diagnosed with Covid in the period, 1.1 per cent of the shielded group caught it. Just 0.01 per cent of the low-risk group died from the virus, compared with 0.51 per cent of the shielders.
Writing in the journal Scientific Reports, the authors concluded that attempts to shield those at highest risk had not been as successful as hoped.
Earlier in the pandemic, some scientists had called for society to operate as normal while the most vulnerable were protected.
But the researchers said that would not have been enough to stop Covid spreading to those at the highest risk, adding that other measures such as masks, social distancing and hand hygiene were crucial to suppressing infections in the general population.
The study also showed that large numbers of deaths during the March to May period had been of moderate risk people who had not been asked to shield.
The authors concluded: "In our study, more than one-quarter of the general population would have needed to be effectively shielded to prevent over 80 per cent of deaths.
"Since this is unlikely to be acceptable at a time when governments are under pressure to avoid further lockdowns, shielding is probably best viewed as an intervention to protect individuals, to be used alongside other population-wide interventions such as physical distancing, face coverings and hand hygiene."