select search filters
briefings
roundups & rapid reactions
before the headlines
Fiona fox's blog
The Office for National Statistics (ONS) have released the latest headline results from their COVID-19 Infection Survey.
Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:
“As it does regularly now, ONS has released the latest headline results from its Coronavirus Infection Survey (CIS) two days before the regular detailed release on Friday. The latest release takes the data up to the week ending 29 January, Saturday last week. I’ve been able to be pretty positive about these headline findings published last week and the week before – in each case they showed downward trends in the estimated numbers who would test positive, compared to the previous week. There were some exceptions for some parts of the UK and some age groups, but generally the pattern was one of decreasing.
“But this week, that’s not true. Really the best I can say is that most of the changes aren’t large, and that things could be much worse. But many of the trends in the numbers who would test positive are now either flat or increasing. Adding up the official estimated numbers testing positive in the four UK countries, the position has barely changed – about 3 million would have tested positive each day in the week ending 22 January, and it’s again about 3 million in the latest week.
“The position varies between the four UK countries. For England, the ONS estimate for the latest week is almost the same as the week before, about 2.6 million people testing positive, which is about 1 in 20 of the population. In Wales and in Northern Ireland ONS estimate that the numbers testing positive were higher in the most recent week than the week before, and the increases are substantial, with estimated numbers for each of those countries being about 40% higher than the week before. The estimates for Northern Ireland and for Wales do tend to be more volatile than for England, because many fewer people are swabbed for the survey in the smaller UK countries. But these are pretty clearly real increases, and rather large ones. For Scotland, ONS estimate that the trend over the most recent two weeks was downwards, but that in the most recent week it was ‘uncertain’.
“The result of these changes is that the estimated rate of testing positive, in the latest week, was about 1 in 20 in both England and Wales, but with a rather higher rate in Northern Ireland, of 1 in 15, and a rather lower rate in Scotland, about 1 in 30. But those are all very high rates of infection compared to the whole pandemic, up to the Omicron-led wave that started late last year. Of course, the consequences of such a high rate are much different from what would have happened earlier in the pandemic, because Omicron is milder than previous variants and because vaccination rates have increased to high levels. But Covid-19 can still affect some people very seriously, and I’d certainly be happier of the infection rates had continued to fall.
“As always, ONS give estimated rates of testing positive for each of the English regions, and for different age groups in England. ONS don’t comment on the trends in those estimates in this headline bulletin – they will say something more about that in the full release on Friday. In any case trends are never as clear as for the whole country, because obviously fewer people are swabbed for the survey in a single region or age group than for the whole country, so the margins of statistical error are considerably wider. But I have compared today’s results with those from a week ago.
“The broad picture for the regions is that the rate of testing positive fell in the latest week, compared to the week before, in the regions in the North of England (North East, North West, Yorkshire and the Humber), and rose in the regions in the South apart from London (so in the East, the South East and the South West). In the Midlands and in London, the changes were smaller. In most of the regions, the change between the latest week and the week before is probably too small to be certain about the underlying trend, given the statistical margins of error – but there were particularly large changes in the North East, where the rate fell by about a quarter, and in the South West, where it rose by about a third.
“The overall picture is one of increases in the regions where infection rates were lowest the week before, and decreases where they were highest. That means that the rates of testing positive are now very uniform across all the regions. ONS say that about 1 in 20 people would test positive in eight of the nine regions, with a rate of 1 in 25 in the East Midlands. Those are all very high infection rates by the standards of the pre-Omicron pandemic. In fact the data look pretty much consistent with the rate being the same in every region. The estimated rate of testing positive in the East Midlands is actually only a very small amount lower than in the East of England or the South East – it just happens to round to 1 in 25 rather than 1 in 20 when ONS round these “1 in so many” rates to the nearest 5, as they always do.
“In terms of age groups in England, roughly speaking the opposite happened compared to the regional picture. Mostly, the age groups where the rate of infection was highest in last week’s release had increases in infection, while those where it was lowest had decreases. Most of the changes in estimated rates were not large (around a tenth, or smaller), and are probably too small to be certain about the direction of movement, given the statistical margins of error.
“The thing that concerns me most is the continuing increases in infection rates in children of school age and younger. The rate in the youngest group, aged from 2 years to school year 6, did not increase anywhere near as much as the previous week, but it did rise again if anything. ONS are still estimating that about 1 in 10 in that age group, as they did last week. For secondary school age children, the rate rose more, by almost a fifth, though ONS are estimating that about 1 in 15 would have tested positive in the most recent week. Those infection rates for children remain really very high, and while very few of them will get really seriously ill, there are still consequences in terms of missing school time or infecting others who are more vulnerable.
“The only other age group where infection rates may have risen, though the trend is not certain, is people aged 35-49. Of course, many people in that age group will have children of school age and younger group – nothing in the CIS data can tell us whether people in their 30s and 40s are being infected by their children, but it’s certainly a possibility. The better news is for the oldest age groups, where, if anything, infection rates reduced in those aged 50-69 and 70+, though the changes are too small to be really sure of the trend.
“For most age groups, ONS’s estimate of the infection rates in “1 in so many” form are the same as the previous week – about 1 in 10 for age 2 to school year 6, 1 in 15 for school years 7 to 11, 1 in 25 for school year 12 to age 24, and 1 in 20 for ages 25-34 and 35-49. For the two oldest groups, the estimated rates have improved a little, from 1 in 35 to 1 in 40 in people aged 50-70 and from 1 in 45 to 1 in 50 in those aged 70+.
“Really, these estimates for age groups are making it even clearer that the pandemic has now become much more an infection of children rather than of older people. A year ago, for example, ONS were estimating that the infection rate in children of secondary school age was about the same as for people aged 50-69. (The rate for the over 70s had started to come down a year ago, partly because vaccination of that age group was under way.) But, for the latest week, ONS estimate that the infection rate in secondary school age children is about three times as high as in the 50-69 group.”
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
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.”