Around nine in ten adults in all parts of the UK are now likely to have Covid-19 antibodies, new figures suggest.
The estimates range from 88.6% in Scotland to 92.6% in Wales, with 90.0% for Northern Ireland and 91.9% for England.
The presence of coronavirus antibodies suggests 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 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 that tests can no longer detect them.
The latest estimates are from the Office for National Statistics (ONS) and are based on a sample of blood test results for the week beginning June 28.
The estimates are for people in private households and do not include settings such as hospitals and care homes.
In England, the latest estimate of 91.9% adults is up from 83.7% a month ago, but there are signs the figures might have levelled off in recent weeks.
In Wales, the estimate is up month-on-month from 86.0% to 92.6%, while in Scotland it is up from 76.8% to 88.6%.
For Northern Ireland the estimate has risen month-on-month from 83.6% to 90.0%.
The figures for these nations also show signs of levelling off in the most recent weeks.
The ONS said there is a clear pattern between vaccination and testing positive for Covid-19 antibodies but “the detection of antibodies alone is not a precise measure of the immunity protection given by vaccination”.
Once infected or vaccinated, the length of time antibodies remain at detectable levels in the blood is not fully known.
It is also not yet known how having detectable antibodies, now or at some time in the past, affects the chance of getting Covid-19 again.
The estimated percentage of adults testing positive for antibodies has continued to increase across all regions of England.
For the week beginning June 28, the estimates range from 89.5% in north-east England to 91.7% in the East Midlands.
Across England as a whole, the highest percentage of adults testing positive for Covid-19 antibodies was estimated to be people aged 50 to 59 (96.9%) while the lowest was 16 to 24-year-olds (67.0%).
In Wales, the highest proportion of adults likely to have tested positive for antibodies were those aged 50 to 59 and 70 to 74 (96.6%), while in Scotland the highest percentage was for people aged 65 to 69 (96.4%).
In Northern Ireland, the ONS uses different age groups due to small sample sizes, and estimates that 96.8% of people aged 50 to 69 were likely to have tested positive for antibodies in the week beginning June 28.