The number of people who have previously had a Covid-19 infection varies “substantially” across the UK, new figures show.

In some regions one person in 20 has previously been infected with coronavirus, according to data from December 2020.

This compares with one in six in other regions, according to a study which measured antibodies in people across the UK.

The Office for National Statistics (ONS) has estimated that 5.4 million people aged 16 and over in England have previously had a Covid-19 infection.

This equates to 12.1% of people over 16, meaning that one in eight adults across the country is thought to have previously been infected.

In Wales, the figure is one in 10, in Scotland one in 11 and in Northern Ireland one in 13.

The ONS estimates that an average of 247,000 people over the age of 16 in Wales have Covid-19 antibodies, with a figure of 398,000 for Scotland and 115,000 in Northern Ireland.

Across England, “there is substantial variation in antibody positivity between regions”, its report states.

The percentage testing positive for Covid-19 antibodies in each region was as follows:

– Yorkshire and the Humber 16.8%– London 16.4%– North West 15.1%– West Midlands 14.3%– East Midlands 12.7%– North East 12.5%– South East 8.3%– East of England 8.1%– South West 4.9%

This means that the South East, East and South West all have rates below the average in England, while others have higher-than-average rates.

The number of people who test positive for antibodies indicates how many people have previously had the infection.

Experts analysed blood samples from people across the UK to come to the conclusions.

But they warned that the length of time Covid-19 antibodies are detectable in the blood is not known.

The ONS study measures antibodies in people who live in private households across the UK. It does not include those in hospitals, care homes or other institutional settings.

Commenting on the figures, Lawrence Young, virologist and professor of molecular oncology at Warwick Medical School, said: “This raises some important questions concerning the possible impact of the UK variant virus on infection rates – this variant is more transmissible and may account for the increased levels of infection as detected by antibodies.

“It is also interesting from the perspective of the vaccine. We are still not sure about the impact of vaccination on the levels and duration of protective immunity in those previously infected with Sars-CoV-2.”