Around seven in 10 older primary school children in most of the UK are likely to have Covid-19 antibodies, new analysis suggests.

The estimates, which are for eight to 11-year-olds, are as high as 72.7% in Scotland, with 71.2% for England and 67.0% in Wales.

Northern Ireland has a slightly lower figure of 63.3%.

The presence of coronavirus antibodies suggests someone has had the infection in the past or has been vaccinated.

But only a tiny number of children aged eight to 11 in the UK outside clinical trials have received any Covid-19 vaccine, meaning almost everyone in this age group with antibodies will have them due to a coronavirus infection.

It takes between two and three weeks after infection – or vaccination – for the human body to make enough antibodies to fight the virus.

Antibodies then remain in the blood at low levels, although these levels can decline over time to the point where tests can no longer detect them.

The figures have been calculated by the Office for National Statistics (ONS) and are based on a sample of blood test results for the week beginning January 10 2022.

They show how antibody levels among older primary school children are likely to have jumped sharply during the recent surge in infections driven by the Omicron variant of coronavirus.

In England the estimate has risen from 55.9% of eight to 11-year-olds at the start of December to 71.2% by early January, while in Scotland it has increased from 55.0% to 72.7%.

Wales has seen a jump from 50.1% to 67.0%, and in Northern Ireland it has risen from 31.4% to 63.3%.

The Joint Committee on Vaccination and Immunisation (JCVI) recommended in December that five to 11-year-olds in clinically vulnerable groups should now be offered two doses of Covid-19 vaccine, delivered eight weeks apart.

This rollout was only just getting under way in the period covered by the latest antibody estimates.

By contrast, first doses of Covid-19 vaccine have been available for 12 to 15-year-olds in the UK since September last year, with jabs being offered in schools as well as local vaccination centres.

Around nine in 10 children in this age group are now likely to have coronavirus antibodies, the ONS found.

Estimates range from 93.3% of those aged 12-15 in Northern Ireland to 90.2% in Wales, with 92.9% in Scotland and 91.9% in England.

All ONS estimates are for people in private households and are subject to uncertainty, given they are based on samples that are part of the wider population.

Antibody positivity is defined by having a fixed concentration of antibodies in the blood.

A negative test result occurs if there are no antibodies, or if antibody levels are too low to reach a threshold at the time of testing.

Levels are expected to decrease over time irrespective of vaccination or natural infection, especially when exposure to the virus is reduced, the ONS said.

This is because our bodies stop making antibodies when they are not needed.