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expert reaction to latest data from the ONS COVID-19 Infection Survey

The Office for National Statistics (ONS) have released the latest data from their COVID-19 Infection Survey.


Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:

“The latest ONS survey of coronavirus infections shows a worsening picture of infection across most of the UK.  While vaccines appear to have dulled the impact of infections on hospitalisation and deaths, the latest data show that infection rates are soaring.

“The ONS survey is a good overview of levels of infection, drawing on a large sample size and with uncertainties and confidence levels clearly expressed in different populations.

“Wales has its highest ever level of infections recorded by the ONS survey.  In England rates are higher than they were at any point during the pre-Christmas 2020 lockdown, and only a few weeks during the New Year peak had higher rates of infections.  The difference now, of course, is that our population is now largely vaccinated.

“The rate of infections among secondary school aged children is clearly the driving force behind this sustained tide of new infections.  Around one in 12 secondary-school aged children had the virus.  This may be of concern to parents, grandparents with caring responsibilities, and teachers, some of whom may not be vaccinated or have health conditions that make them vulnerable to serious disease from covid infection.

“By contrast, infections among young adults aged 16 to 24 remains relatively low, which is likely a result of vaccinations in this age group.

“The vaccine rollout was praised this week by the otherwise scathing Select Committee report into the UK’s response to the pandemic.  With infection rates going up, and little appetite for new restrictions on movement or activities, vaccines appear to be our best hope of avoiding more trouble ahead.  With so much covid in the population, we must hope that the jabs continue to protect most people against serious disease.”


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

“Last week I wrote a pretty downbeat comment on what the latest results from the ONS Covid-19 Infection Survey (CIS) were telling us about the state of the pandemic.  This week’s CIS release takes the data up to the week 3-9 October, and looking at the overall picture across the UK, I find the position even more concerning than last week.  Indeed most of the points that I made last week still apply this week, often more strongly than they did last week.  Across the whole UK, the official ONS estimated number of people who would test positive for the virus that causes Covid-19 on a representative day in the week ending 9 October was just over a million, about 8% higher than the previous week.

“As has been the case for some time, the picture is different across the four UK countries.  My main concern is about the rates of testing positive in England and in Wales.  ONS estimate that the positivity rate increased in both those countries in the most recent week, to about 1 in 60 in the community population (aged 2 and over) in England and about 1 in 45 in Wales.  The Welsh estimate is subject to a fairly wide margin of statistical error, because the number of people swabbed for the survey there is much smaller than in England, but the figures and margins of error do pretty clearly indicate that the positivity rate is higher in Wales than in England.  Positivity rates have been rising in England since early September, and for much longer than that (essentially since May) in Wales.  In Wales, the estimated rate of testing positive is now higher than it has been in every week since the CIS began there in July 2020.  In England, looking back over the whole set of CIS weekly estimates since the survey began in April 2020, there have only been four weeks when the estimated positivity rate was higher than it is for the most recent week.  Those four weeks ran from 27 December 2020 to 23 January 2021, when the second wave of the pandemic was at its horrible height.

“Of course I’m not saying that things are as bad now as they were back in January this year.  Vaccinations have made a huge difference to the chance that an infection will lead to hospitalisation or, worse, to death.  But that doesn’t mean that the current infection rate isn’t concerning.

“Things look, on average, better in Scotland and in Northern Ireland.  ONS estimate that the rate of testing positive for the virus continued to fall in Scotland, as it has been doing for about a month now, and the estimate for the latest week is that about 1 in 80 people in the Scottish community population would test positive.  That is encouraging.  The position in Northern Ireland is a bit less clear, partly because the statistical margin of error around the estimates is higher in Northern Ireland than in the other UK countries because the number of people swabbed for the survey is smaller there.  ONS estimate that the positivity rate fell there in the two weeks to October 9, though they say that trend in the most recent week is ‘uncertain’.  The estimated rate of testing positive in Northern Ireland for the most recent week is 1 in 120.  Even allowing for the wide margin of error, that’s a considerably lower rate than in England or Wales, and probably also lower than the Scottish rate too, though the margins of error on both the Scottish and the Northern Irish estimates mean that we can’t be entirely certain that the rate is lower in Northern Ireland.

“It’s not difficult to see what’s continuing to drive up infection rates in England, particularly, and in Wales, if one looks at the estimated rates of testing positive for separate age groups.  The ONS bulletin provides more, and more precise, detail on rates in age groups for England than for the other UK countries.  That’s because the numbers swabbed for the survey in England within a single age group are greater than in the other countries – though they are still smaller than for the whole of England so margins of error are wider.  ONS estimate, for England, that the rate of testing positive increased for those in school years 7 to 11 (secondary school age), ages 50 to 69, and in those aged 70 and over.  There have been some increase, they estimate, over the past two weeks in children younger than secondary school age (2 years old to school year 6) and in those aged 35-49, but the rate of increase has been slower and ONS say the trends in those groups are ‘uncertain’ in the most recent week.  The position in the remaining two age groups (school year 12 to age 24, and 25-34) is less clear.

“But all this detail shouldn’t distract from the fact that the rate of testing positive is very much higher in children on secondary school age (school years 7 to 11) than in every other age group.  In secondary school ages, at the end of August, about 1 in 40 in England would have tested positive.  ONS estimate that the rate in that age group started shooting upwards from about 10 September, and for the latest week they estimate that about 1 in every 10 would test positive.  That is extraordinarily high.  Last week’s estimate was 1 in 15, which was bad enough, and that’s a considerable rise in one week.  (But see my technical note under “Further information” below, which explains that the rise is about 17% in a week, not as large as a change from 1 in 15 to 1 in 10 might imply, but still a huge change.)

“It’s not good news that the rates in the oldest age groups may be increasing too, but they are still very low by comparison with the secondary school ages, at 1 in 130 for those aged 50-69 and 1 in 160 for the over 70s.  The great majority in those two age groups will have been double vaccinated, and some of them will already have had booster vaccinations.

“Looking at it another way, some ball-park calculations indicate that almost a third of all people, who would have tested positive in England in the week 3-9 October, are in that single age group, school years 7 to 11.  Including younger children from age 2 to the end of primary school as well, that would account for over half of all the infections in the country.  Of course, if children in those age groups do become infected, the chance of them becoming seriously ill is much smaller than for older people.  But that chance is not zero.  And there are other possible consequences for them, such as long Covid.  The indications are that that is less likely for children than for older age groups, particularly for the younger children.  But one set of ONS estimates, also based on CIS data is that around one in twenty of children aged 12-16, who tested positive for the virus, would go on to have symptoms consistent with long Covid, as much as 12 weeks after it.  And, of course, teenagers can certainly pass on an infection to their older relatives.

“The position, by age group, is somewhat less clear in the other UK countries because of the statistical imprecisions, but the picture in Wales does appear to be generally similar to England.  Infections in children of secondary school age have dominated the pandemic there, and are doing so more and more.  That age group did also dominate in Scotland until the first or second week in September, but the number of infections in that age group has fallen back considerably since then.  The position is less clear-cut in Northern Ireland.

“The obvious reasons for the difference between England and Wales on one hand, and Scotland on the other, are that schools opened in Scotland about a month before they did in England, so that infection levels in school children have had more time to stabilise (for whatever reason), and that the rate of vaccinating that age group in Scotland has been considerably greater than in England.  There may be other reasons too, of course.  But, whatever the exact mix of reasons, Scotland looks to be in a much better position than England or Wales as we move into the colder times of the year, when all respiratory infections, including Covid-19, generally have more impact.  Given that the policy in England and Wales (as in Scotland and Northern Ireland) is to offer one vaccine dose to everyone aged 12 and over, we’ve really got to move on quickly with vaccinating those aged 12 to 15 across the whole UK.

“Finally, I’ll mention briefly the position in the regions of England.  ONS estimate that the positivity rate was increasing in the most recent week, in six of the nine English regions.  In the other three (North East, East Midlands and London) the trend in the most recent week was uncertain.  The latest estimated rates of testing positive are rather more uniform across the whole country than they have often been recently, with ONS estimated rates between 1 in 50 and 1 in 60 in six of the nine regions, slightly lower in two regions (East of England at 1 in 65 and South East at 1 in 75), and lower still in London (1 in 100).  But in general those estimates have fairly wide margins of error, so neither the trends nor the exact positivity rates are all that certain.

“I should mention that the swabs from the ONS CIS are sent for testing to three Lighthouse Labs, in Milton Keynes, Liverpool and Glasgow, so not to the private lab which appears to have been producing too many false results, so I don’t think there’s any reason to be concerned about changes in the accuracy of the CIS results.

Further information:

“Technical point: I prefer to quote these positivity rates as “1 in n” because I think they may be easier to understand than giving them as percentages.  However, once the rate has got this high, there is a possible snag.  ONS round their “1 in n” estimates to the nearest 5 (provided n is less than 100).  This makes sense provided the infection rates are not extremely high, because there is always statistical uncertainty in the estimates.  But perhaps it causes issues when infection rates do get extremely high.  For instance, in estimated percentages testing positive, the latest week’s figure for the school year 7 to year 11 group is 8.10%, which works out to 1 in 12.4 testing positive, and ONS rounded that to 1 in 10.  The week before, the percentage estimate was 6.93%, which (unrounded) is 1 in 14.4, and ONS rounded this to 1 in 15.  Working with the percentages, the positivity rate in that age group went up by 17% between those two weeks, but working with ONS’s rounded “1 in n” figures, the increase looks considerably larger – it appears to have increased by half in a week.  But any way you look at it, that is a considerable rise in just one week.”


Prof Jim Naismith, Director of the Rosalind Franklin Institute, and Professor of Structural Biology, University of Oxford, said:

“There is some good news from today’s ONS release (to 9th October), the prevalence in Scotland continues to fall slowly.  Less good news, is that prevalence in England has increased to around 1 in 60.

“England seems to be heading where Scotland was at the start of September, if this is so (nothing is certain) there will be a continuing rise in positive cases over the next few weeks.

“Certainly the daily 7 day average indicates another swell.

“Whilst a deal of ink is spilled on the differences between the UK nation’s and the small differences in policy, the variation within England’s regions exceeds the difference between the nations.

“Explanations of fault or prescience really have to explain all the data – if you claim to know why Scotland is better or worse than Wales or England etc., then your explanation has to explain why London is better or worse than Leeds.

“I am very troubled by the continued rise in the cases of children, aged to 12 to 17 with covid19. We are fast approaching and may have reached 1 in 10 of this age group with covid19.

“If this is a deliberate policy, it would be good to explain to the public (including me) the cost benefit ratio behind it.  Some of these children will be harmed by long covid19.

“If it is not deliberate, then some immediate mitigation measures (masking, ventilation) would seem desirable.  I know vaccination is being rolled out and this will halt this wave, but it takes time.

“With winter approaching, it might be worthwhile to take stock of where we are.

“The UK has had at least three waves.  The first in March 2020 hit the UK harder than most countries.  In hindsight, it is unarguable that locking down even a week earlier would have saved lives.

“The second wave which really began in the early autumn of 2020, hit us once again extremely hard.  Once again it is unarguable different choices would have reduced the death toll.

“As we approached last Christmas, things looked very threatening for the country.  Without the vaccination campaign then underway in the UK, we would have started 2021 in a dreadful state, much worse than the first wave due to Delta.

“Sadly, at the moment the UK has a higher level of covid19 (third wave) than most other comparable countries, this is seen not just in positive tests but in hospital admissions and deaths.

“We should remember that around 1000 people die of covid every week in the UK, each of those deaths represents a tragedy.

“High case numbers will mean more long covid19.

“The strong start in vaccination has faded and the UK now lags several comparable countries in the EU.  The UK is still ahead in vaccine coverage than many other countries, including the USA.

“The data from Israel indicate the third jab is extremely effective.

“The data from Merck indicates that there is, I hope, going to be an effective pill to reduce serious harm from infection.

“We are once again in a less than ideal situation as we head into this winter.

“The concern is not of death run riot, but of long covid blighting lives and an NHS overwhelmed.

“The more vaccination and the less spread of the virus will make for a happier winter for everyone.

“I am double vaccinated, waiting for my third, I test twice a week with LFD, I wear mask at work, and on public transport and socialise outside whenever I can.”



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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