Covid-19 antibody levels among UK adults remain at a record high, with no evidence of a drop among older age groups whose most recent dose of vaccine was likely to be several months ago, analysis suggests.

Some 99.3% of people aged 80 and over in England were likely to have antibodies at the start of March, along with 98.2% in Wales and 98.3% in Scotland – the highest for each nation since estimates began at the end of 2020.

The figures, which have been calculated by the Office for National Statistics (ONS), also estimate 99.2% of over-70s in Northern Ireland had antibodies at the beginning of this month – again, the highest level so far.

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

It takes between two and three weeks after infection – or vaccination – for the human body to make enough antibodies to fight Covid-19, but levels are expected to decrease over time, especially when exposure to the virus is reduced, the ONS said.

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

The estimates, which are for the week ending March 6, suggest levels remain high across the adult population, including among those older age groups whose most recent dose of Covid-19 vaccine might be up to six months ago.

This is likely to reflect the lasting effect of the booster campaign that began in autumn 2021, but also the surge in coronavirus infections in December and January caused by the Omicron variant.

Prevalence of the virus has remained high since then, with many people continuing to catch the virus – particularly in recent weeks, which have seen a further sharp increase in infections driven by the Omicron BA.2 variant.

Bookings opened this week in England for people aged 75 and over to receive a “spring booster” – a fourth dose of vaccine – with similar campaigns set to begin in the rest of the UK.

The Joint Committee on Vaccination and Immunisation (JCVI) has advised that a spring jab should be offered to those most vulnerable to Covid-19 as a precautionary measure, six months after their most recent dose.

Some 99.0% of all adults in England were estimated to have Covid-19 antibodies at the start of March, up from 77.4% at the start of December 2021, the ONS found.

The equivalent figures for Wales show a jump from 72.7% to 98.9%, while in Scotland levels have risen from 77.4% to 99.0%.

Northern Ireland has seen an increase from 80.8% to 98.8%.

All ONS estimates are based on a sample of blood test results from 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 the threshold at the time of testing.