More than 400,000 people in England had their Covid risk over-estimated by the NHS because of an over-cautious algorithm.
The QCovid algorithm, used to help identify who should be shielding or getting early access to vaccines, automatically put people into higher risk categories when data was missing, health news site Pulse reported.
If their weight wasn't recorded they were assumed to be obese and if their ethnicity was missing they were filed under black – both of which would assume someone was at a higher-than-average risk of severe Covid-19.
Doctors in York double-checking isolation lists said they found 110 cases where patients had been wrongly asked to stay at home and shield.