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expert reaction to headline results from the ONS COVID-19 Infection Survey

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


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

“The ONS survey is a much more reliable source of information than apps and other sources of infection data, due to its high sample numbers and consistent statistical approach.

“It shows that in the past week around 4.3 million people were infected in the UK, many of whom will have been walking around in their daily lives, spreading the disease without realising it before developing symptoms, or without being affected at all.  If they don’t know they’ve got the coronavirus, they can’t take appropriate measures to stop themselves spreading it.  It is particularly concerning that these numbers are substantially higher than the data on the government’s Coronavirus dashboard, which paints a somewhat rosier picture.  With so much pressure on the PCR testing system and patchy reporting of LFT results, the ONS is a more reliable indicator of the state of play.

“A number of reports over the past week have used the dashboard data to fanfare a levelling off and even fall of infection numbers, but these data show a different picture.  By this measure it is true that the rate of increase has slowed, but has not stopped climbing and the numbers have certainly not started to fall.”


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

“ONS continues its current policy of publishing the headline results from its Coronavirus Infection Survey (CIS) a couple of days before the main release on Fridays.  Today’s headline release covers the week ending 6 January in most of the UK, but the week ending 7 January in Scotland – I don’t know the reason for the slight difference, but roughly speaking they are all about the first week in 2022.

“Overall, ONS’s estimate for the number of people aged 2 and over in the UK community population who would test positive on a day in that week was 4,300,700.  That’s an increase of 15% on the estimate for the week before.  It’s unwelcome that the numbers were still rising, but the increase was considerably smaller than the previous week, when the estimated count went up by almost two thirds (64%) compared to the week before that.  So, just possibly, an early sign that things are going to improve and level off, even if that hasn’t happened just yet.

“In every one of the four UK countries, the estimated rate of testing positive for the latest week was higher than for the week before, though for all four, the week-on-week increase was smaller than it had been for the last week of 2021 compared to the week before that.  The rates of infection in England and in Wales increased by smaller percentages than did the rates in Scotland and Northern Ireland.  The upshot is that ONS are still estimating that the infection rate was highest in England out of all four countries, at about 1 in every 15 people testing positive, but the rates in the other three countries are similar to one another (and still very high) at about 1 in 20.

“As usual, there are also results for individual regions and separate age groups in England (though not for age groups within individual regions).  Because a single region or age group contains many fewer people than the whole country, and hence fewer people are swabbed for the survey in a region or age group than for the whole of England, there’s more statistical uncertainty about the region and age group figures, so short-term trends there mustn’t be over-interpreted.

“On regions, there’s some encouraging news that the estimated rate of testing positive fell in London for the latest week compared to the week before, by 11%.  That’s not a huge fall, and it could be a bit smaller (or indeed larger) because of the statistical uncertainty.  And we can’t tell whether it will continue in future weeks.  We’ve got to remember that there will be more mixing, and so probably more transmission of infection, as schools reopen and people go back to work after the holidays.  That would not all be picked up yet in the latest CIS data, which go up only to 3 January.  But I’ll take the results as encouraging anyway.  The estimated rate of testing positive in the latest week in London is about 1 in 15, though, which is still one of the higher rates across all the regions.

“In the other regions, the picture is mixed.  The estimated infection rate changed very little in the East of England compared to the week before.  Allowing for statistical uncertainty, it’s safest to say that the trend is not very certain there, but that’s better than the rapid increases we’ve seen there in recent previous weeks.  The infection rate continued to increase in the other region close to London, the South East, but the increase there was slower than the English average.  But the increases in all the other regions for the most recent week were at least 20%, and more than that in Yorkshire and the Humber (nearly 40%) and the North East (nearly 45%).

“As a result of these changes, the highest estimated infection rate across all the English regions is for the North West, where about 1 in every 10 people would have tested positive in the latest week.  The rate in Yorkshire and the Humber is also about 1 in 10.  The lowest estimate is for the South West, about 1 in 25, and the rates in the East and South East are also relatively low at about 1 in 20.  The remaining four regions (North East, East Midlands, West Midlands, London) have estimates of about 1 in 15.

“I should say, though, that the rate for every English region is still very high.  An important issue is the rate at which this will feed through to severe illness, hospitalisation, or, sadly, deaths.  High vaccination rates have kept the rates of severe illness at much lower levels than in previous major infection waves.

“However, the news isn’t so encouraging on one other aspect that seems to have kept serious Covid down since Omicron arrived.  Infection rates have been highest in younger people, who are less likely to become severely ill.  This week’s CIS results for age groups in England show some signs that Omicron infection may be getting considerably more prevalent in older people.  Omicron is certainly very dominant now across the UK.

“Infection rates in the youngest age group (age 2 to school year 6) fell a little in the latest week compared to the week before, and there was also a very small possible fall in the 35-49 age group.  Rates increased in the other younger age groups between school year 7 and 34 years of age, but more slowly than the England average increase.  However, the estimated rate of testing positive went up much more in the older groups, by about 30% in the 50-69 group and by about 40% in those aged 70 and over.

“The result of these movements is that the highest estimated rates in the latest week are still in the younger groups, at about 1 in 10 in the groups between school year 12 and age 34, and about 1 in 15 for school age and younger children and for those aged 35-49.  But the rate of testing positive in the 50-69 group is not all that much less, at about 1 in 20, and the estimate for the 70+ group is now about 1 in 30, compared to 1 in 45 just a week earlier.  However, changes in mixing patterns as people go back to work and school might lead to things looking different, one way or another, in next week’s results.

“Today’s figures relate to a period including some of the Christmas and New Year holidays, when potential biases and interpretation difficulties in the confirmed cases numbers on the Government dashboard at were quite severe.  That’s because the dashboard numbers were affected by late publication of some results, on top of the usual problems that they can be affected by changes in the types and numbers of people being tested, reporting of lateral flow results, availability of tests, and so on.  None of that affects the CIS, where a representative sample of people is tested, regardless of symptoms, purely to track infection levels.”



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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