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expert reaction to the latest fortnightly release on the COVID-19 Infection Survey looking at antibody and vaccination data for the UK, 22 June 2021

The Office for National Statistics (ONS) have released the latest report from the COVID-19 infection survey, looking at antibody and vaccination data for the UK.


Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:

“The latest fortnightly ONS release on antibodies and vaccinations in the UK community population provides more evidence of the success of the vaccination programme.  It shows a continuing increase in the numbers of people who test positive for antibodies to the virus that can cause Covid-19.  The data now go up to the week ending 10 June for the antibody data (and 12 June for the vaccination data).  Two weeks before that, about 80% of adults aged 16 and over would have tested positive for antibodies in England, Wales and Northern Ireland, though slightly fewer in Scotland (about 70%).  Now that figure is over 85%, something like six in every seven, in England, Wales and Northern Ireland, and slightly lower (about 80% or four in five) in Scotland.  Since these figures come from a survey, they are subject to some inevitable statistical uncertainty – but the increases are big enough to be definitely real.  The people tested for the ONS survey form a reasonably representative sample of the population, and appropriate adjustments are made to deal with any remaining lack of representativeness, so I wouldn’t expect any major biases.

“These data can’t tell you why the percentage positive for antibodies is lower in Scotland than in the other countries, but it is very likely to be simply because a smaller proportion of the Scottish population was ever infected with the virus.  Over the whole pandemic, about 7,200 people out of every 100,000 in England have had confirmed cases of Covid-19, according to the dashboard at, and the figures for Wales and Northern Ireland are not much smaller (6,800 for every 100,000 in Wales, 6,600 in Northern Ireland).  But in Scotland, only 4,700 in every 100,000 people have been confirmed cases.  The antibody results in this ONS release can’t distinguish between people who have antibodies because they were infected, and people who have antibodies because they were vaccinated.  The percentage of the population that has been vaccinated is slightly lower in Scotland than in the other three UK countries, according to the data in this ONS bulletin and other sources, but that difference is too small to explain the lower percentage of people with antibodies in the Scottish population, and that must have more to do with the lower number of people who have been infected during the pandemic.

“ONS rightly emphasise, however, that testing positive for antibodies isn’t the same as being immune.  There are other aspects of the immune system, particularly cell-based immunity, that antibodies don’t measure.  And it’s possible that antibody levels that are too small to detected by the ONS survey’s blood tests might still contribute to immunity.  So testing for antibodies can’t give a precise measure of levels of immunity.  It’s also not really possible, from these data, to get an idea of how antibody levels might decrease (‘wane’) after infection or vaccination, and how long that might take, because, to do that properly, one would need more information on when people were infected or vaccinated than these data provide.

“We already know from other sources, such as regular reports from the NHS and on the dashboard at, that the number of people vaccinated is all the UK countries is continuing to increase rapidly.  The estimates of percentages vaccinated in this bulletin are not the same as those from the other sources, for reasons described in the bulletin – but you do have to bear in mind that the rates given in sources like the dashboard are based on population estimates that might not always be accurate, particularly for small areas.  However, the percentage of the population that has had at least one vaccine dose has continued to increase in each of the UK countries.  That’s particularly true for those aged 25-34, where the rate has shot up in recent weeks, and in the latest week in these data, around two-thirds of that age group have had at least one vaccine dose (even more in Northern Ireland).  Those increases in vaccination haven’t clearly shown corresponding increases in antibody positivity yet, but that is probably because it takes a couple of weeks after vaccination for antibodies to develop, and it will be less than two weeks after vaccination for many in that age group.

“What I think is particularly important is that the percentage of people who have had two vaccine doses has increased pretty rapidly in all four UK countries since the previous bulletin two weeks ago.  Investigations of vaccine effectiveness against severe disease, particularly involving the Delta variant, have shown how important it is to have both doses.  That percentage does differ quite a lot between the countries for the latest week – it’s about 67%, or two-thirds of the population aged 16+, in England, about 60% (three in five) in Northern Ireland, and about 50% (half) in Wales and Scotland.  For people aged over about 60, the great majority have had two jabs in all four countries – the difference is in younger age groups.  In England, nearly nine in ten of those aged 50-59 have had two doses, but it’s only about seven in ten in Scotland and Wales (and the figures for Northern Ireland aren’t very precise for that age group, because the number of people tested in the survey is smaller).”


Prof Paul Hunter, Professor in Medicine, UEA, said:

“The latest report from ONS on the antibody prevalence survey covers the period 7th to 10th June and so lags behind the current situation by about a week or two.  The most obvious findings are that in all the age groups over 34 for England the modelled percentage of people with antibodies is over 90% and in the 60 to 79 age groups it is over 95%.  This is remarkably high rate and most of this will be due to the impact of vaccine.  What is perhaps even more reassuring is that in the rate of people aged 25 to 34 is 69% and aged 16 to 24 is 56%.  Given than vaccination has only been offered to all adults in the past few days much of the 16 to 24 age group will have acquired their antibodies from natural infection, only 25% of this group has had a single dose vaccine by the 10th June and somewhat fewer of those would have had their dose long enough ago to have generated antibodies.

“Whilst immunity to COVID infection is not guaranteed in people with antibodies the presence of antibody is strongly correlated with at least some degree of protection.  So this is very good news, even for younger age groups in that a substantial proportion (probably even the majority) of those younger age groups already have some degree of protection.

“Unfortunately this study tells us nothing about antibody in children under 16.”



All our previous output on this subject can be seen at this weblink:



Declared interests

Prof Kevin McConway: “I am a Trustee of the SMC and a member of its Advisory Committee.  I am also a member of the Public Data Advisory Group, which provides expert advice to the Cabinet Office on aspects of public understanding of data during the pandemic.  My quote above is in my capacity as an independent professional statistician.”

None others received.

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