More than half of adults in the UK are now likely to have Covid-19 antibodies, new figures have suggested.
The estimates range from 57.8% of adults in Scotland to 68.3% in England, with 61.0% for Wales and 62.5% for Northern Ireland.
The presence of Covid-19 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 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 ending April 11.
They reflect the ongoing impact of the vaccine rollout across the UK, in particular the increasing number of people who have received both doses and are now fully vaccinated.
Government figures show that by April 11, 32,190,576 first doses of vaccine had been given – the equivalent of 61.1% of adults – along with 7,656,205 second doses (14.5% adults).
The ONS said that across all four nations 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 ONS estimates are for people in private households and do not include settings such as hospitals and care homes.
Responding to the figures, Health Secretary Matt Hancock said: “Today’s ONS data shows more and more of us are benefiting from protection the vaccine gives us against this awful disease.
“The public’s response to the call to vaccines has been amazing, with over 95% of over-50s stepping forward. We can now see the impact in reality.
“The evidence is clear that the vaccine protects you, your loved ones and those around you. The vaccine is our way out and getting back to doing the things we have missed. This is a massive national effort – so when you get the call, get the jab.”
In England, the highest percentage of adults testing positive for Covid-19 antibodies in the week to April 11 was estimated to be the 70 to 74 age group (87.6%), followed by 80 and over (87.1%) and 60 to 64 (85.7%).
The lowest percentage was for 16 to 24-year-olds (46.5%).
In Wales, the highest proportion of adults likely to have tested positive for antibodies was the 70 to 74 age group (83.0%) followed by 65 to 69 (82.9%), while in Scotland the highest percentage was among 65 to 69-year-olds (85.1%), followed by 70 to 74-year-olds (81.4%).
In Northern Ireland, the ONS uses different age groups due to small sample sizes and estimates 82.0% of people aged 70 and over were likely to have tested positive for antibodies in the week to April 11.